Semiconductor chip assembly with welded metal pillar and enlarged plated contact terminal

ABSTRACT

A semiconductor chip assembly includes a semiconductor chip that includes a conductive pad, a conductive trace that includes a routing line, a metal pillar and an enlarged plated contact terminal, a connection joint that electrically connects the routing line and the pad, and an encapsulant. The chip and the metal pillar are embedded in the encapsulant, the routing line extends laterally beyond the metal pillar towards the chip, the metal pillar is welded to the routing line and includes a ball bond and a stem, and the plated contact terminal is plated on the stem.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.11/472,703 filed Jun. 22, 2006, now U.S. Pat. No. 7,268,421, which is acontinuation of U.S. application Ser. No. 10/985,579 filed Nov. 10,2004, now U.S. Pat. No. 7,071,573.

This application also claims the benefit of U.S. Provisional ApplicationSer. No. 60/784,034 filed Mar. 20, 2006.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor chip assembly, and moreparticularly to a semiconductor chip assembly with a welded metal pillarand its method of manufacture.

2. Description of the Related Art

Semiconductor chips have input/output pads that must be connected toexternal circuitry in order to function as part of an electronic system.The connection media is typically an array of metallic leads (e.g., alead frame) or a support circuit (e.g., a substrate), although theconnection can be made directly to a circuit panel (e.g., a motherboard). Several connection techniques are widely used. These includewire bonding, tape automated bonding (TAB) and flip-chip bonding.

Wire bonding is by far the most common and economical connectiontechnique. In this approach, wires are bonded, one at a time, from thechip to external circuitry by thermocompression, thermosonic orultrasonic processes. In thermocompression bonding, fine gold wire isfed from a spool through a clamp and a capillary. A thermal source isswept past an end of the wire to form a wire ball that protrudes fromthe capillary. The chip or capillary is then heated to about 200 to 300°C., the capillary is brought down over an aluminum pad, the capillaryexerts pressure on the wire ball, and the wire ball forms a ball bond onthe pad. The capillary is then raised and moved to a terminal on thesupport circuit, the capillary is brought down again, and thecombination of force and temperature forms a wedge bond between the wireand the terminal. Thus, the connection between the pad and the terminalincludes the ball bond (which only contacts the pad), the wedge bond(which only contacts the terminal) and the wire between the bonds. Afterraising the capillary again, the wire is ripped from the wedge bond, thethermal source is swept past the wire to form a new wire ball, and theprocess is repeated for other pads on the chip. Thermosonic bonding issimilar to thermocompression bonding but adds ultrasonic vibration asthe ball and wedge bonds are formed so that less heat is necessary.Ultrasonic bonding uses aluminum wire to form wedge bonds withoutapplying heat. There are many variations on these basic methods.

TAB involves bonding gold-bumped pads on the chip to external circuitryon a polymer tape using thermocompression bonding. TAB requiresmechanical force such as pressure or a burst of ultrasonic vibration andelevated temperature to accomplish metallurgical welding between thewires or bumps and the designated surface.

Flip-chip bonding involves providing pre-formed solder bumps on thepads, flipping the chip so that the pads face down and are aligned withand contact matching bond sites, and melting the solder bumps to wet thepads and the bond sites. After the solder reflows it is cooled down andsolidified to form solder joints between the pads and the bond sites.Organic conductive adhesive bumps with conductive fillers in polymerbinders have been used in place of solder bumps, but they do notnormally form a metallurgical interface in the classical sense. A majoradvantage of flip-chip bonding over wiring bonding and TAB is that itprovides shorter connection paths between the chip and the externalcircuitry, and therefore has better electrical characteristics such asless inductive noise, cross-talk, propagation delay and waveformdistortion. In addition, flip-chip bonding requires minimal mountingarea and weight which results in overall cost saving since no extrapackaging and less circuit board space are used.

While flip-chip technology has tremendous advantages over wire bondingand TAB, its cost and technical limitations are significant. Forinstance, the cost of forming bumps on the pads is significant. Inaddition, an adhesive is normally underfilled between the chip and thesupport circuit to reduce stress on the solder joints due to thermalmismatch between the chip and the support circuit, and the underfillingprocess increases both manufacturing complexity and cost.

Other techniques besides wire bonding, TAB and flip-chip technologieshave been developed to provide connection joints that electricallyconnect pads on chips to external conductive traces. These connectionjoints can be formed by electroplated metal, electrolessly plated metal,solder or conductive adhesive.

Electroplating provides deposition of an adherent metallic coating ontoa conductive object placed into an electrolytic bath composed of asolution of the salt of the metal to be plated. Using the terminal as ananode (possibly of the same metal as the one used for plating), a DCcurrent is passed through the solution affecting transfer of metal ionsonto the cathode surface. As a result, the metal continuallyelectroplates on the cathode surface. Electroplating using AC currenthas also been developed. Electroplating is relatively fast and easy tocontrol. However, a plating bus is needed to supply current whereelectroplating is desired. The plating bus creates design constraintsand must be removed after the electroplating occurs. Non-uniform platingmay arise at the bottom of relatively deep through-holes due to poorcurrent density distribution. Furthermore, the electrolytic bath isrelatively expensive.

Electroless plating provides metal deposition by an exchange reactionbetween metal complexes in a solution and a catalytic metal thatactivates or initiates the reaction. As a result, the electroless metalcontinually plates (i.e., deposits or grows) on the catalytic metal.Advantageously, the reaction does not require externally appliedelectric current. Therefore, electroless plating can proceed without aplating bus. However, electroless plating is relatively slow.Furthermore, the electroless bath is relatively expensive.

Solder joints are relatively inexpensive, but exhibit increasedelectrical resistance as well as cracks and voids over time due tofatigue from thermo-mechanical stresses. Further, the solder istypically a tin-lead alloy and lead-based materials are becoming farless popular due to environmental concerns over disposing of toxicmaterials and leaching of toxic materials into ground water supplies.

Conductive adhesive joints with conductive fillers in polymer bindersare relatively inexpensive, but do not normally form a metallurgicalinterface in the classical sense. Moisture penetration through thepolymer binder may induce corrosion or oxidation of the conductivefiller particles resulting in an unstable electrical connection.Furthermore, the polymer binder and the conductive filler may degradeleading to an unstable electrical connection. Thus, the conductiveadhesive may have adequate mechanical strength but poor electricalcharacteristics.

Accordingly, each of these connection joint techniques has variousadvantages and disadvantages. The optimal approach for a givenapplication depends on design, reliability and cost considerations.

The semiconductor chip assembly is subsequently connected to anothercircuit such as a printed circuit board (PCB) or mother board duringnext level assembly. Different semiconductor assemblies are connected tothe next level assembly in different ways. For instance, ball grid array(BGA) packages contain an array of solder balls, and land grid array(LGA) packages contain an array of metal pads that receive correspondingsolder traces on the PCB.

Thermo-mechanical wear or creep of the solder joints that connect thesemiconductor chip assembly to the next level assembly is a major causeof failure in most board assemblies. This is because non-uniform thermalexpansion and/or contraction of different materials causes mechanicalstress on the solder joints.

Thermal mismatch induced solder joint stress can be reduced by usingmaterials having a similar coefficient of thermal expansion (CTE).However, due to large transient temperature differences between the chipand other materials during power-up of the system, the induced solderjoint stress makes the assembly unreliable even when the chip and theother materials have closely matched thermal expansion coefficients.

Thermal mismatch induced solder joint stress can also be reduced byproper design of the support circuit. For instance, BGA and LGA packageshave been designed with pillar post type contact terminals that extendabove the package and act as a stand-off or spacer between the packageand the PCB in order to absorb thermal stress and reduce solder jointfatigue. The higher the aspect ratio of the pillar, the more easily thepillar can flex to follow expansion of the two ends and reduce shearstress.

Conventional approaches to forming the pillar either on a wafer or aseparate support circuit include a bonded interconnect process (BIP) andplating using photoresist.

BIP forms a gold ball on a pad of the chip and a gold pin extendingupwardly from the gold ball using a thermocompression wire bonder.Thereafter, the gold pin is brought in contact with a molten solder bumpon a support circuit, and the solder is reflowed and cooled to form asolder joint around the gold pin. A drawback to this approach is thatwhen the wire bonder forms the gold ball on the pad it appliessubstantial pressure to the pad which might destroy active circuitrybeneath the pad. In addition, gold from the pin can dissolve into thesolder to form a gold-tin intermetallic compound which mechanicallyweakens the pin and therefore reduces reliability.

U.S. Pat. No. 5,722,162 discloses fabricating a pillar by electroplatingthe pillar on a selected portion of an underlying metal exposed by anopening in photoresist and then stripping the photoresist. Although itis convenient to use photoresist to define the location of the pillar,electroplating the pillar in an opening in the photoresist has certaindrawbacks. First, the photoresist is selectively exposed to light thatinitiates a reaction in regions of the photoresist that correspond tothe desired pattern. Since photoresist is not fully transparent andtends to absorb the light, the thicker the photoresist, the poorer thepenetration efficiency of the light. As a result, the lower portion ofthe photoresist might not receive adequate light to initiate or completethe intended photo-reaction. Consequently, the bottom portion of theopening in the photoresist might be too narrow, causing a pillar formedin the narrowed opening to have a diameter that decreases withdecreasing height. Such a pillar has a high risk of fracturing at itslower portion in response to thermally induced stress. Furthermore,photoresist residue on the underlying metal might cause the pillar tohave poor quality or even prevent the pillar from being formed. Second,if the photoresist is relatively thick (such as 100 microns or more),the photoresist may need to be applied with multiple coatings andreceive multiple light exposures and bakes, which increases cost andreduces yield. Third, if the photoresist is relatively thick, theelectroplated pillar may be non-uniform due to poor current densitydistribution in the relatively deep opening. As a result, the pillar mayhave a jagged or pointed top surface instead of a flat top surface thatis better suited for providing a contact terminal for the next levelassembly.

In view of the various development stages and limitations in currentlyavailable semiconductor chip assemblies, there is a need for asemiconductor chip assembly that is cost-effective, reliable,manufacturable, versatile, provides a vertical conductor with excellentmechanical and electrical properties, and makes advantageous use theparticular connection joint technique best suited for a givenapplication.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a semiconductor chipassembly with a chip and a conductive trace that provides a low cost,high performance, high reliability package.

Another object of the present invention is to provide a convenient,cost-effective method for manufacturing a semiconductor chip assembly.

Generally speaking, the present invention provides a semiconductor chipassembly that includes a semiconductor chip that includes a conductivepad, a conductive trace that includes a routing line, a metal pillar andan enlarged plated contact terminal, a connection joint thatelectrically connects the routing line and the pad, and an encapsulant.The chip and the metal pillar are embedded in the encapsulant, therouting line extends laterally beyond the metal pillar towards the chip,the metal pillar is welded to the routing line and includes a ball bondand a stem, and the plated contact terminal is plated on the stem.

Generally speaking, the present invention also provides a method ofmaking a semiconductor chip assembly that includes mechanicallyattaching a semiconductor chip that includes a conductive pad to arouting line, forming a connection joint that electrically connects therouting line and the pad, welding a metal pillar that includes a ballbond and a stem to the routing line, wherein the routing line extendslaterally beyond the metal pillar towards the chip, forming anencapsulant after attaching the chip to the routing line and welding themetal pillar to the routing line, wherein the chip and the metal pillarare embedded in the encapsulant, and then plating an enlarged platedcontact terminal on the stem.

In accordance with an aspect of the invention, a semiconductor chipassembly includes a semiconductor chip that includes first and secondopposing surfaces, wherein the first surface of the chip includes aconductive pad, a conductive trace that includes a routing line, a metalpillar and a plated contact terminal, wherein the metal pillar ismetallurgically welded to and only to the routing line and consists of aball bond and an elongated stem, the ball bond is welded to the routingline, the stem extends from the ball bond, is spaced from the routingline and includes a distal end that faces away from the ball bond, andthe plated contact terminal is plated on and only on the distal end, aconnection joint that electrically connects the routing line and thepad, and an encapsulant that includes first and second opposingsurfaces, wherein the first surface of encapsulant faces in a firstdirection, the second surface of the encapsulant faces in a seconddirection opposite the first direction, the chip and the metal pillarare embedded in the encapsulant, the chip, the metal pillar and theencapsulant extend vertically beyond the routing line in the firstdirection, the routing line extends laterally beyond the metal pillartowards the chip and extends vertically beyond the chip and the metalpillar in the second direction, the metal pillar is disposed outside aperiphery of the chip and extends vertically across most or all of athickness of the chip between the first and second surfaces of the chip,the stem extends vertically beyond the ball bond in the first directionand extends vertically farther than the ball bond, the distal end islaterally aligned with the first surface of the encapsulant and disposedwithin a periphery of the plated contact terminal, and the platedcontact terminal extends vertically beyond the chip, the metal pillarand the encapsulant in the first direction, has a dome-like shape withan apex that faces in the first direction and has a diameter that is atleast twice as large as a diameter of the distal end.

The chip can be the only chip embedded in the encapsulant, oralternatively, multiple chips can be embedded in the encapsulant. Thefirst surface of the chip can face in the first direction and the secondsurface of the chip can face in the second direction, or alternatively,the first surface of the chip can face in the second direction and thesecond surface of the chip can face in the first direction.

The routing line can be disposed vertically beyond the chip and themetal pillar in the second direction. The routing line can extend withinand outside the periphery of the chip, or alternatively, be disposedoutside the periphery of the chip. Furthermore, the routing line can bein an electrically conductive path between the metal pillar and any chipembedded in the encapsulant. That is, any chip embedded in theencapsulant can be electrically connected to the metal pillar by anelectrically conductive path that includes the routing line.

The metal pillar can extend vertically beyond the chip in the firstdirection, and can extend vertically beyond the chip in the seconddirection. The metal pillar can extend across most or all of a thicknessof any chip embedded in the encapsulant. Likewise, the metal pillar canextend vertically beyond any chip embedded in the encapsulant in thefirst and second directions, and can be disposed outside the peripheryof any chip embedded in the encapsulant.

The metal pillar can be disposed within a periphery of the routing lineand within a periphery of the plated contact terminal. Furthermore, themetal pillar can be spaced from any electrical conductor other than therouting line and the plated contact terminal, and can be spaced from anymaterial other than the routing line, the plated contact terminal andthe encapsulant.

The metal pillar can be not covered in the first direction by theencapsulant or any other insulative material of the assembly. Forinstance, the plated contact terminal can be exposed in the firstdirection, and the metal pillar can be covered in the first direction bythe plated contact terminal. The metal pillar can also be not covered inthe second direction by the encapsulant or any other insulative materialof the assembly. For instance, a solder terminal that is electricallyconnected to the metal pillar can be exposed in the second direction,and the metal pillar can be covered in the second direction by thesolder terminal.

The ball bond can be disposed within a periphery of the plated contactterminal and can have a diameter that is at least twice as large as adiameter of the stem, and at least twice as large as a diameter of thedistal end.

The stem can be disposed within a periphery of the ball bond and can bestraight, have a uniform diameter and extend across most or all of thethickness of the chip.

The plated contact terminal can be an electroplated metal or anelectrolessly plated metal. The plated contact terminal can have adiameter that is at least twice as large as a diameter of the ball bond,at least four times as large as a diameter of the stem, and at leastfour times as large as a diameter of the distal end. Furthermore, theplated contact terminal can have a hemispherical shape that includes aconvex surface and a flat surface, the convex surface can include theapex and be spaced from the metal pillar and the encapsulant, and theflat surface can contact the metal pillar and the encapsulant.

The encapsulant can contact the chip, the ball bond, the stem and theplated contact terminal. The encapsulant can cover the chip in the firstdirection, or alternatively, the first surface of the encapsulant can belaterally aligned with the second surface of the chip and the secondsurface of the chip can be not covered in the first direction by anothermaterial of the assembly.

The connection joint can contact and electrically connect the routingline and the pad. The connection joint can be electroplated metal,electrolessly plated metal, solder, conductive adhesive or a wire bond.

The assembly can include an insulative base that contacts the routingline, is spaced from and overlapped by the chip and extends verticallybeyond the chip, the metal pillar and the encapsulant in the seconddirection.

The assembly can include an insulative adhesive that contacts the chipand extends vertically beyond the chip in the second direction.

The assembly can include a solder terminal that is electricallyconnected to the routing line, extends vertically beyond the routingline and the encapsulant in the second direction and is spaced from themetal pillar and the connection joint.

The assembly can include a tapered pillar that contacts and is notmetallurgically welded to the routing line, is disposed outside theperiphery of the chip, is overlapped by the metal pillar and extendsvertically beyond the chip, the routing line, the metal pillar and theencapsulant in the second direction. The tapered pillar can bevertically aligned with the metal pillar. The tapered pillar can includefirst and second opposing surfaces that are flat and parallel to oneanother and tapered sidewalls therebetween, wherein the first surface ofthe tapered pillar faces towards and contacts the routing line, thesecond surface of the tapered pillar faces away from and is spaced fromthe routing line, and the tapered sidewalls slant inwardly towards thesecond surface of the tapered pillar. Furthermore, the second surface ofthe tapered pillar can be concentrically disposed within a surface areaof the first surface of the tapered pillar, and a surface area of thefirst surface of the tapered pillar can be at least 20 percent largerthan a surface area of the second surface of the tapered pillar.

The assembly can include a heat sink that is mechanically attached tothe chip, electrically isolated by the chip, overlapped by the chip anddisposed vertically beyond the chip and the conductive trace in thesecond direction.

The assembly can include a ground plane that is mechanically attached tothe routing line, electrically connected to the routing line, overlappedby the routing line and disposed vertically beyond the chip and therouting line in the second direction.

The assembly can be a first-level package that is a single-chip ormulti-chip package.

In accordance with another aspect of the invention, a method of making asemiconductor chip assembly includes providing a routing line, thenmechanically attaching a semiconductor chip to the routing line, whereinthe chip includes first and second opposing surfaces, and the firstsurface of the chip includes a conductive pad, forming a connectionjoint that electrically connects the routing line and the pad,metallurgically welding a metal pillar to and only to the routing line,wherein the metal pillar consists of a ball bond and an elongated stem,the ball bond is welded to the routing line and the stem extends fromthe ball bond and is spaced from the routing line, forming anencapsulant after attaching the chip to the routing line and welding themetal pillar to the routing line, wherein the encapsulant includes afirst surface that faces in a first direction and a second surface thatfaces in a second direction opposite the first direction, the chip andthe metal pillar are embedded in the encapsulant, the encapsulant coversand extends vertically beyond the chip, the routing line and the metalpillar in the first direction, the chip and the metal pillar extendvertically beyond the routing line in the first direction, the routingline extends laterally beyond the metal pillar towards the chip andextends vertically beyond the chip and the metal pillar in the seconddirection, the metal pillar is disposed outside a periphery of the chipand extends vertically across most or all of a thickness of the chipbetween the first and second surfaces of the chip, and the stem extendsvertically beyond the ball bond in the first direction and extendsvertically farther than the ball bond, removing a portion of theencapsulant such that a distal end of the stem is exposed, and thenplating a plated contact terminal on and only on the distal end, whereinthe plated contact terminal extends vertically beyond the chip, themetal pillar and the encapsulant in the first direction, covers thedistal end in the first direction and has a diameter that is at leasttwice as large as a diameter of the distal end.

The method can include forming the routing line by selectivelydepositing the routing line on a metal base, and attaching the chip tothe routing line such that the metal base extends vertically beyond thechip in the second direction.

The method can include forming the routing line by providing a platingmask on the metal base, wherein the plating mask includes an openingthat exposes a portion of the metal base, and then electroplating therouting line on the exposed portion of the metal base through theopening in the plating mask.

The method can include etching the metal base after forming theencapsulant, thereby reducing contact area between the metal base andthe routing line. Etching the metal base can remove a first portion ofthe metal base that contacts the routing line without removing a secondportion of the metal base that contacts the routing line, therebyreducing but not eliminating contact area between the metal base and therouting line. For instance, etching the metal base can remove a firstportion of the metal base within a periphery of the pad without removinga second portion of the metal base outside the periphery of the pad. Asanother example, etching the metal base can form a tapered pillar froman unetched portion of the metal base that contacts the routing line, isdisposed outside the periphery of the chip, is overlapped by the metalpillar and extends vertically beyond the chip, the routing line, themetal pillar and the encapsulant in the second direction. Alternatively,etching the metal base can eliminate contact area between the metal baseand the routing line. For instance, etching the metal base can removethe metal base.

The method can include etching the metal base after forming theencapsulant, thereby electrically isolating the routing line from otherrouting lines formed on the metal base. Likewise, the method can includeetching the metal base after forming the encapsulant, therebyelectrically isolating the pad from other conductive pads of the chip.

The method can include welding the metal pillar to the routing line bythermocompression bonding, thermosonic bonding or ultrasonic bonding.Welding the metal pillar to the routing line can also include applyingball bonding using a capillary that presses a wire ball against therouting line. For instance, welding the metal pillar to the routing linecan include positioning the capillary with the wire ball extendingtherefrom over the routing line, wherein the wire ball is connected to awire that is fed through the capillary, moving the capillary towards therouting line so that the wire ball contacts the routing line and deformsinto the ball bond and remains connected to the wire, moving thecapillary away from the routing line so that the wire extends from theball bond, fracturing the wire beyond proximity to the ball bond todetach the wire from the stem, and cooling the ball bond so that theball bond contacts and is welded to and electrically connected to therouting line.

The method can include removing the portion of the encapsulant bygrinding, laser ablation or plasma etching. For instance, removing theportion of the encapsulant can include grinding the encapsulant withoutgrinding the stem, and then grinding the encapsulant and the stem.Furthermore, removing the portion of the encapsulant can includegrinding the encapsulant without grinding the stem, and then grindingthe encapsulant and the stem and exclude grinding the chip, oralternatively, grinding the encapsulant without grinding the stem, thengrinding the encapsulant and the stem without grinding the chip, andthen grinding the encapsulant, the stem and the chip.

The method can include removing the portion of the encapsulant to exposethe distal end, expose the second surface of the chip, laterally alignthe distal end and the first surface of the encapsulant, laterally alignthe distal end and the second surface of the chip, laterally align thefirst surface of the encapsulant and the second surface of the chipand/or laterally align the distal end, the first surface of theencapsulant and the second surface of the chip. In any case, the chipand the metal pillar remain embedded in the encapsulant.

The method can include plating the plated contact terminal on the distalend by electroplating or electroless plating. For instance, the methodcan include electroplating the plated contact terminal on the distal endusing the metal base, the routing line and the metal pillar as a platingbus before etching the metal base, or alternatively, electrolesslyplating the plated contact terminal on the distal end after etching themetal base.

The method can include forming the connection joint by plating theconnection joint on the routing line and the pad. For instance, theconnection joint can be electroplated or electrolessly plated on therouting line and the pad. Alternatively, the method can include formingthe connection joint by depositing a non-solidified material on therouting line and the pad and then hardening the non-solidified material.For instance, solder paste can be deposited on the routing line and thepad and then hardened by reflowing, or conductive adhesive can bedeposited on the routing line and the pad and then hardened by curing.Alternatively, the method can include forming the connection joint bywire bonding. For instance, the wire bond can extend vertically beyondthe chip and the routing line in the first direction when the firstsurface of the chip faces in the first direction, or alternatively, thewire bond can extend vertically beyond the chip, the routing line andthe metal pillar in the second direction when the first surface of thechip faces in the second direction.

The method can include attaching the chip to the routing line and thenwelding the metal pillar to the routing line, or alternatively, weldingthe metal pillar to the routing line and then attaching the chip to therouting line.

The method can include forming the connection joint and then welding themetal pillar to the routing line, or alternatively, welding the metalpillar to the routing line and then forming the connection joint.

The method can include forming the connection joint and then forming theencapsulant, or alternatively, forming the encapsulant and then formingthe connection joint.

The method can include forming the connection joint and then plating theplated contact terminal on the distal end, or alternatively, plating theplated contact terminal on the distal end and then forming theconnection joint.

The method can include providing an insulative base that contacts therouting line, is spaced from and overlapped by the chip and extendsvertically beyond the chip, the metal pillar and the encapsulant in thesecond direction.

The method can include providing an insulative adhesive that attachesthe chip to the routing line before forming the encapsulant.

The method can include providing a solder terminal that is electricallyconnected to the routing line, extends vertically beyond the routingline and the encapsulant in the second direction and is spaced from themetal pillar and the connection joint. For instance, the solder terminalcan be deposited on and in contact with the routing line, oralternatively, a plated terminal can be electrolessly plated on and incontact with the routing line, and then the solder terminal can bedeposited on and in contact with the plated terminal and spaced from therouting line.

An advantage of the present invention is that the semiconductor chipassembly can be manufactured conveniently and cost effectively. Anotheradvantage is that the metal base or the insulative base can be providedbefore the encapsulant, thereby enhancing the mechanical support andprotection for the routing line after the chip and the metal pillar areattached. Another advantage is that the metal pillar can be welded tothe routing line rather than deposited on the routing line byelectroplating or electroless plating which improves uniformity andreduces manufacturing time and cost. Another advantage is that theconnection joint can be made from a wide variety of materials andprocesses, thereby making advantageous use of mature connection jointtechnologies in a unique and improved manufacturing approach. Anotheradvantage is that the assembly need not include connection joints thatare wire bonds or TAB leads, although the process is flexible enough toaccommodate these techniques if desired. Another advantage is that themetal pillar can extend across most or all of a thickness of the chipand the plated contact terminal and the solder terminal can protrudevertically from the encapsulant and the insulative base, respectively,thereby facilitating a three-dimensional stacked arrangement. Anotheradvantage is that the assembly can be manufactured using low temperatureprocesses which reduces stress and improves reliability. A furtheradvantage is that the assembly can be manufactured using well-controlledprocesses which can be easily implemented by circuit board, lead frameand tape manufacturers. Still another advantage is that the assembly canbe manufactured using materials that are compatible with copper chip andlead-free environmental requirements.

These and other objects, features and advantages of the invention willbe further described and more readily apparent from a review of thedetailed description of the preferred embodiments which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description of the preferred embodiments can bestbe understood when read in conjunction with the following drawings, inwhich:

FIGS. 1A-19A are cross-sectional views showing a method of making asemiconductor chip assembly in accordance with a first embodiment of thepresent invention;

FIGS. 1B-19B are top plan views corresponding to FIGS. 1A-19A,respectively;

FIGS. 1C-19C are bottom plan views corresponding to FIGS. 1A-19A,respectively;

FIGS. 7D-7H are cross-sectional views showing a method of making a metalpillar for a semiconductor chip assembly in accordance with the firstembodiment of the present invention;

FIGS. 20A, 20B and 20C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with asecond embodiment of the present invention;

FIGS. 21A, 21B and 21C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with athird embodiment of the present invention;

FIGS. 22A, 22B and 22C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with afourth embodiment of the present invention;

FIGS. 23A, 23B and 23C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with afifth embodiment of the present invention;

FIGS. 24A, 24B and 24C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with asixth embodiment of the present invention;

FIGS. 25A, 25B and 25C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with aseventh embodiment of the present invention;

FIGS. 26A, 26B and 26C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with aneighth embodiment of the present invention;

FIGS. 27A, 27B and 27C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with aninth embodiment of the present invention;

FIGS. 28A, 28B and 28C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with atenth embodiment of the present invention;

FIGS. 29A, 29B and 29C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with aneleventh embodiment of the present invention;

FIGS. 30A, 30B and 30C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with atwelfth embodiment of the present invention;

FIGS. 31A, 31B and 31C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with athirteenth embodiment of the present invention;

FIGS. 32A, 32B and 32C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with afourteenth embodiment of the present invention;

FIGS. 33A, 33B and 33C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with afifteenth embodiment of the present invention; and

FIGS. 34A, 34B and 34C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with asixteenth embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1A-19A, 1B-19B and 1C-19C are cross-sectional, top and bottomviews, respectively, of a method of making a semiconductor chip assemblyin accordance with a first embodiment of the present invention.

FIGS. 1A, 1B and 1C are cross-sectional, top and bottom views,respectively, of semiconductor chip 110 which is an integrated circuitin which various transistors, circuits, interconnect lines and the likeare formed (not shown). Chip 110 includes opposing major surfaces 112and 114 and has a thickness (between surfaces 112 and 114) of 150microns. Surface 112 is the active surface and includes conductive pad116 and passivation layer 118.

Pad 116 is substantially aligned with passivation layer 118 so thatsurface 112 is essentially flat. Alternatively, if desired, pad 116 canextend above or be recessed below passivation layer 118. Pad 116provides a bonding site to electrically couple chip 110 with externalcircuitry. Thus, pad 116 can be an input/output pad or a power/groundpad. Pad 116 has a length and width of 100 microns.

Pad 116 has an aluminum base that is cleaned by dipping chip 110 in asolution containing 0.05 M phosphoric acid at room temperature for 1minute and then rinsed in distilled water. Pad 116 can have the aluminumbase serve as a surface layer, or alternatively, pad 116 can be treatedto include a surface layer that covers the aluminum base, depending onthe nature of a connection joint that shall subsequently contact thesurface layer. In this embodiment, the connection joint is a gold wirebond. Therefore, pad 116 need not be treated to accommodate thisconnection joint. Alternatively, pad 116 can be treated by depositingseveral metal layers, such as chromium/copper/gold ortitanium/nickel/gold on the aluminum base. The chromium or titaniumlayer provides a barrier for the aluminum base and an adhesive betweenthe overlaying metal and the aluminum base. The metal layers, however,are typically selectively deposited by evaporation, electroplating orsputtering using a mask which is a relatively complicated process.Alternatively, pad 116 can be treated by forming a nickel surface layeron the aluminum base. For instance, chip 110 can be dipped in a zincsolution to deposit a zinc layer on the aluminum base. This step iscommonly known as zincation. Preferably, the zinc solution containsabout 150 grams/liter of NaOH, 25 grams/liter of ZnO, and 1 gram/literof NaNO₃, as well as tartaric acid to reduce the rate at which thealuminum base dissolves. Thereafter, the nickel surface layer iselectrolessly deposited on the zincated aluminum base. A suitableelectroless nickel plating solution is Enthone Enplate NI-424 at 85° C.

Chip 110 includes many other pads on surface 112, and only pad 116 isshown for convenience of illustration. In addition, chip 110 has alreadybeen singulated from other chips that it was previously attached to on awafer.

FIGS. 2A, 2B and 2C are cross-sectional, top and bottom views,respectively, of metal base 120 which includes opposing major surfaces122 and 124. Metal base 120 is a copper plate with a thickness of 200microns.

FIGS. 3A, 3B and 3C are cross-sectional, top and bottom views,respectively, of photoresist layers 126 and 128 formed on metal base120. Photoresist layers 126 and 128 are deposited using a dry filmlamination process in which hot rolls simultaneously press photoresistlayers 126 and 128 onto surfaces 122 and 124, respectively. A reticle(not shown) is positioned proximate to photoresist layer 126.Thereafter, photoresist layer 126 is patterned by selectively applyinglight through the reticle, applying a developer solution to remove thephotoresist portion rendered soluble by the light, and then hard baking,as is conventional. As a result, photoresist layer 126 contains anopening that selectively exposes surface 122 of metal base 120, andphotoresist layer 128 remains unpatterned. Photoresist layers 126 and128 each have a thickness of 50 microns beyond surfaces 122 and 124,respectively.

FIGS. 4A, 4B and 4C are cross-sectional, top and bottom views,respectively, of routing line 130 formed on metal base 120.

Routing line 130 includes elongated routing portion 132 and enlargedcircular portion 134. Elongated routing portion 132 and enlargedcircular portion 134 are adjacent to and integral with and coplanar withone another.

Routing line 130 is composed of a first nickel layer electroplated onmetal base 120, a copper layer electroplated on the first nickel layer,a second nickel layer electroplated on the copper layer, and a goldlayer electroplated on the second nickel layer. The first nickel layercontacts and is sandwiched between metal base 120 and the copper layer,the copper layer contacts and is sandwiched between the first and secondnickel layers, the second nickel layer contacts and is sandwichedbetween the copper layer and the gold layer, and the gold layer contactsthe second nickel layer. Thus, the copper layer, second nickel layer andgold layer are spaced and separated from metal base 120, the secondnickel layer and gold layer are spaced and separated from the firstnickel layer, the gold layer is exposed, and the copper layer and firstand second nickel layers are buried beneath the gold layer. Forconvenience of illustration, the copper layer, gold layer and first andsecond nickel layers are shown as a single layer.

Routing line 130 is formed by an electroplating operation usingphotoresist layers 126 and 128 as plating masks. Thus, routing line 130are formed additively. Initially, a plating bus (not shown) is connectedto metal base 120, current is applied to the plating bus from anexternal power source, and metal base 120 is submerged in anelectrolytic nickel plating solution such as Technic Techni Nickel “S”at room temperature. As a result, the first nickel layer electroplates(deposits or grows) on the exposed portion of surface 122. The firstnickel electroplating operation continues until the first nickel layerhas the desired thickness. Thereafter, the structure is removed from theelectrolytic nickel plating solution and submerged in an electrolyticcopper plating solution such as Sel-Rex CUBATH M™ at room temperaturewhile current is applied to the plating bus to electroplate the copperlayer on the first nickel layer. The copper electroplating operationcontinues until the copper layer has the desired thickness. Thereafter,the structure is removed from the electrolytic copper plating solutionand submerged in an electrolytic nickel plating solution such as TechnicTechni Nickel “S” at room temperature while current is applied to theplating bus to electroplate the second nickel layer on the copper layer.The second nickel electroplating operation continues until the secondnickel layer has the desired thickness. Thereafter, the structure isremoved from the electrolytic nickel plating solution and submerged inan electrolytic gold plating solution such as Technic Orotemp at roomtemperature while current is applied to the plating bus to electroplatethe gold layer on the second nickel layer. The gold electroplatingoperation continues until the gold layer has the desired thickness.Thereafter, the structure is removed from the electrolytic gold platingsolution and rinsed in distilled water to remove contaminants.

Routing line 130 has a thickness of 26.5 microns. In particular, thefirst and second nickel layers each have a thickness of 3 microns, thecopper layer has a thickness of 20 microns, and the gold layer has athickness of 0.5 microns. Elongated routing portion 132 is a flat planarlead with a width (orthogonal to its elongated length) of 100 microns,and enlarged circular portion 134 has a diameter of 400 microns.

FIGS. 5A, 5B and 5C are cross-sectional, top and bottom views,respectively, of metal base 120 and routing line 130 after photoresistlayers 126 and 128 are stripped. Photoresist layers 126 and 128 areremoved using a solvent, such as a mild alkaline solution with a pH of9, that is highly selective of photoresist with respect to copper,nickel and gold. Therefore, no appreciable amount of metal base 120 orrouting line 130 is removed.

FIGS. 6A, 6B and 6C are cross-sectional, top and bottom views,respectively, of solder mask 136 formed on metal base 120 and routingline 130.

Solder mask 136 is initially a photoimageable liquid resin that isdispensed on metal base 120 and routing line 130. Thereafter, soldermask 136 is patterned by selectively applying light through a reticle(not shown), applying a developer solution to remove the solder maskportions rendered soluble by the light, and then hard baking, as isconventional. As a result, solder mask 136 contains opening 138 with adiameter of 300 microns that is vertically aligned with and selectivelyexposes enlarged circular portion 134. Solder mask 136 exposes an innercircular region of enlarged circular portion 134 with a diameter of 300microns, and covers an outer annular region of enlarged circular portion134 with a width of 50 microns ((400−300)/2). In addition, solder mask136 extends 30 microns upwardly beyond routing line 130.

FIGS. 7A, 7B and 7C are cross-sectional, top and bottom views,respectively, of metal pillar 140 welded to routing line 130.

Metal pillar 140 is metallurgically welded to routing line 130 bythermosonic bonding. Metal pillar 140 contacts and is electricallyconnected to the inner circular region of enlarged circular portion 134,extends into opening 138, and is spaced from metal base 120, elongatedrouting portion 132 and solder mask 136. Metal pillar 140 extendsupwardly beyond routing line 130 by 475 microns and is disposed withinthe periphery of enlarged circular portion 134. Furthermore, metal base120 and routing line 130 are disposed downwardly beyond metal pillar140.

Metal pillar 140 consists of ball bond 150 and stem 152. Ball bond 150is metallurgically welded to routing line 130 and has a height of 35microns and a diameter of 60 microns, and stem 152 is an elongatedstraight dangling wire segment with a height of 440 microns and auniform diameter of 25 microns that is adjacent to and integral with andextends vertically from ball bond 150 and is spaced from routing line130. Thus, metal pillar 140 is an open-ended wire bond and stem 152extends vertically farther than ball bond 150 by about 400 microns(440−35).

FIGS. 7D-7H are cross-sectional views of a method of making metal pillar140.

FIG. 7D shows the structure with capillary 142 and wire ball 144positioned above opening 138 and wire ball 144 spaced from routing line130 and disposed outside opening 138. Capillary 142 is part of aconventional thermosonic wire bonding apparatus. Capillary 142 has aconical shape and can be composed of alumina, tungsten carbide, ceramic,artificial ruby or various refractory metals. Wire ball 144 is composedof gold and protrudes from the bottom of capillary 142. Wire ball 144 isformed at the end of gold wire 146 by applying thermal energy, such aselectronic flame-off or a hydrogen gas flame jet, as is conventional.Wire 146 is fed from a spool (not shown) through clamp 148 and a bore incapillary 142. Clamp 148 is closed to hold wire 146 in place. Wire ball144 has a diameter of 50 microns, and wire 146 has a diameter of 25microns.

FIG. 7E shows the structure after capillary 142 moves downward and wireball 144 enters opening 138 and contacts routing line 130. Since opening138 has a diameter of 300 microns and extends 30 microns above routingline 130, and wire ball 144 has a diameter of 50 microns and is centeredwith respect to opening 138, wire ball 144 contacts routing line 130without contacting solder mask 136. Clamp 148 opens before the movementbegins so that wire 146 unwinds from its spool as capillary 142 moves.In addition, capillary 142 is heated to about 150 to 200° C. andprovides horizontal ultrasonic oscillatory motions with a frequency ofabout 60 to 120 kHz. The combination of heat from capillary 142 and therecent flaming operation place wire ball 144 in a soft state which iseasy to deform. However, the temperature of wire ball 144 does not reachthe glass transition temperature of solder mask 136 which remains asolid insulative film.

FIG. 7F shows the structure after capillary 142 moves further downwardtowards routing line 130 such that wire ball 144 deforms into ball bond150 that contacts routing line 130 in opening 138. More particularly,since wire ball 144 is still in a soft state which is easy to deform,and capillary 142 exerts a downward force of about 25 to 45 grams whilecontinuing to oscillate ultrasonically, wire ball 144 deforms into ballbond 150. Clamp 148 remains open so that wire 146 continues to unwindfrom its spool as capillary 142 moves. The combination of heat, pressureand ultrasonic vibration welds routing line 130 and ball bond 150.Furthermore, solder mask 136 prevents ball bond 150 from contactingmetal base 120 in the event misregistration occurs.

FIG. 7G shows the structure after capillary 142 moves upward and awayfrom routing line 130 and ball bond 150 while clamp 148 remains open andwire 146 slides through capillary 142 without exerting upward pressureon ball bond 150. In addition, ball bond 150 begins to cool andsolidify.

FIG. 7H shows the structure after ball bond 150 solidifies, clamp 148closes and capillary 142 moves upward to fracture wire 146 over but wellbeyond ball bond 150, thereby detaching wire 146 from stem 152. As aresult, metal pillar 140 is composed of ball bond 150 and stem 152 andis welded to routing line 130.

Conductive trace 154 includes routing line 130 and metal pillar 140.Conductive trace 154 is adapted for providing horizontal and verticalrouting between pad 116 and a next level assembly.

FIGS. 8A, 8B and 8C are cross-sectional, top and bottom views,respectively, of adhesive 156 formed on metal base 120.

Adhesive 156 may include an organic surface protectant such as HK 2000which is promptly applied to the structure after metal pillar 140 isformed to reduce native oxide formation on the exposed copper surfaces.The use of organic surface protectant layers in insulative adhesives forsemiconductor chip assemblies is well-known in the art.

Thereafter, a liquid resin (A stage) such as polyamic acid is appliedover metal base 120 using stencil printing. During stencil printing, astencil (not shown) is placed over metal base 120, routing line 130 andsolder mask 136, a stencil opening is aligned with metal base 120 andoffset from routing line 130 and solder mask 136, and then a squeegee(not shown) pushes the liquid resin along the surface of the stencilopposite metal base 120, routing line 130 and solder mask 136, throughthe stencil opening and onto metal base 120 but not routing line 130 andsolder mask 136. The liquid resin is compliant enough at roomtemperature to conform to virtually any shape. Therefore, the liquidresin flows over and covers a portion of metal base 120 but remainsspaced and separated from routing line 130, solder mask 136 and metalpillar 140.

FIGS. 9A, 9B and 9C are cross-sectional, top and bottom views,respectively, of chip 110 mechanically attached to metal base 120,routing line 130, solder mask 136 and metal pillar 140 by adhesive 156.

Adhesive 156 extends between and contacts chip 110 and metal base 120but remains spaced and separated from routing line 130, solder mask 136and metal pillar 140. Surface 112 of chip 110 faces upwardly and awayfrom metal base 120 and routing line 130 and is exposed, and surface 114of chip 110 faces downwardly and towards metal base 120 and is coveredby adhesive 156. Chip 110 and metal base 120 do not contact one another,and chip 110 and routing line 130 do not contact one another.

Adhesive 156 is sandwiched between chip 110 and metal base 120 usingrelatively low pressure from a pick-up head that places chip 110 onadhesive 156, holds chip 110 against adhesive 156 for 5 seconds and thenreleases chip 110. The pick-up head is heated to a relatively lowtemperature such as 150° C., and adhesive 156 receives heat from thepick-up head transferred through chip 110. As a result, adhesive 156proximate to chip 110 is partially polymerized (B stage) and forms a gelbut is not fully cured, and adhesive 156 that is partially polymerizedprovides a loose mechanical bond between chip 110 and metal base 120.

Chip 110 and metal base 120 are positioned relative to one another sothat chip 110 is disposed within the periphery of adhesive 156, androuting line 130, solder mask 136 and metal pillar 140 are disposedoutside the periphery of chip 110. Chip 110 and metal base 120 can bealigned using an automated pattern recognition system.

Thereafter, the structure is placed in an oven and adhesive 156 is fullycured (C stage) at relatively low temperature in the range of 200 to250° C. to form a solid adhesive insulative thermosetting polyimidelayer that contacts and is sandwiched between and mechanically attacheschip 110 and metal base 120. Adhesive 156 is 5 microns thick betweenchip 110 and metal base 120.

At this stage, metal base 120 covers and extends downwardly beyond chip110, routing line 130, solder mask 136, metal pillar 140 and adhesive156, routing line 130 is disposed outside the periphery of chip 110,extends laterally beyond metal pillar 140 towards chip 110 and extendsdownwardly beyond chip 110 and metal pillar 140, metal pillar 140 isdisposed outside the periphery of chip 110, extends vertically acrossmost of the thickness of chip 110 (between surfaces 112 and 114),extends upwardly beyond chip 110 and is disposed upwardly beyond andoverlaps routing line 130, and adhesive 156 extends downwardly beyondchip 110. Furthermore, chip 110 remains electrically isolated fromrouting line 130.

FIGS. 10A, 10B and 10C are cross-sectional, top and bottom views,respectively, of connection joint 158 formed on pad 116 and routing line130.

Connection joint 158 is a gold wire bond that is ball bonded to pad 116and then wedge bonded to routing line 130. Thus, connection joint 158contacts and electrically connects pad 116 and routing line 130, andconsequently, electrically connects pad 116 and metal pillar 140.Furthermore, connection joint 158 extends within and outside theperiphery of chip 110, extends upwardly beyond chip 110 by 100 micronsand is spaced and separated from metal pillar 140.

FIGS. 11A, 11B and 11C are cross-sectional, top and bottom views,respectively, of encapsulant 160 formed on chip 110, routing line 130,solder mask 136, metal pillar 140, adhesive 156 and connection joint158.

Encapsulant 160 is deposited by transfer molding. Transfer molding isthe most popular chip encapsulation method for essentially all plasticpackages. Generally speaking, transfer molding involves formingcomponents in a closed mold from a molding compound that is conveyedunder pressure in a hot, plastic state from a central reservoir calledthe transfer pot through a tree-like array of runners and gates intoclosed cavities. Molding compounds are well-known in the art.

The preferred transfer molding system includes a preheater, a mold, apress and a cure oven. The mold includes an upper mold section and alower mold section, also called “platens” or “halves” which define themold cavities. The mold also includes the transfer pot, runners, gatesand vents. The transfer pot holds the molding compound. The runners andgates provide channels from the transfer pot to the cavities. The gatesare placed near the entrances of the cavities and are constricted tocontrol the flow and injection velocity of the molding compound into thecavities and to facilitate removal of the solidified molding compoundafter molding occurs. The vents allow trapped air to escape but aresmall enough to permit only a negligible amount of the molding compoundto pass through them.

The molding compound is initially in tablet form. The preheater applieshigh-frequency energy to preheat the molding compound to a temperaturein the range of 50 to 100° C. The preheated temperature is below thetransfer temperature and therefore the preheated molding compound is notin a fluid state. In addition, the structure is placed in one of themold cavities, and the press operates hydraulically to close the moldand seal the mold cavities by clamping together the upper and lower moldsections. Guide pins ensure proper mating of the upper and lower moldsections at the parting line. In addition, the mold is heated to atransfer temperature in the range of 150 to 250° C. by insertingelectric heating cartridges in the upper and lower mold sections.

After closing the mold, the preheated molding compound in tablet form isplaced in the transfer pot. Thereafter, a transfer plunger appliespressure to the molding compound in the transfer pot. The pressure is inthe range of 10 to 100 kgf/cm² and preferably is set as high as possiblewithout introducing reliability problems. The combination of heat fromthe mold and pressure from the transfer plunger converts the moldingcompound in the transfer pot into a fluid state. Furthermore, thepressure from the transfer plunger forces the fluid molding compoundthrough the runners and the gates into the mold cavities. The pressureis maintained for a certain optimum time to ensure that the moldingcompound fills the cavities.

The lower mold section contacts and makes sealing engagement with and isgenerally flush with metal base 120. However, the upper mold section isspaced from metal pillar 140 by 100 microns. As a result, the moldingcompound contacts the exposed portions of the chip 110, metal base 120,solder mask 136, metal pillar 140, adhesive 156 and connection joint 158in the cavity. After 1 to 3 minutes at the transfer temperature, themolding compound polymerizes and is partially cured in the mold.

Once the partially cured molding compound is resilient and hard enoughto withstand ejection forces without significant permanent deformation,the press opens the mold, ejector pins remove the molded structure fromthe mold, and excess molding compound attached to the molded structurethat solidified in the runners and the gates is trimmed and removed. Themolded structure is then loaded into a magazine and postcured in thecuring oven for 4 to 16 hours at a temperature somewhat lower than thetransfer temperature but well above room temperature to completely curethe molding compound.

The molding compound is a multi-component mixture of an encapsulatingresin with various additives. The principal additives include curingagents (or hardeners), accelerators, inert fillers, coupling agents,flame retardants, stress-relief agents, coloring agents and mold-releaseagents. The encapsulating resin provides a binder, the curing agentprovides linear/cross-polymerization, the accelerator enhances thepolymerization rate, the inert filler increases thermal conductivity andthermal shock resistance and reduces the thermal coefficient ofexpansion, resin bleed, shrinkage and residual stress, the couplingagent enhances adhesion to the structure, the flame retardant reducesflammability, the stress-relief agent reduces crack propagation, thecoloring agent reduces photonic activity and device visibility, and themold-release agent facilitates removal from the mold.

Encapsulant 160 contacts and covers chip 110, metal base 120, soldermask 136, metal pillar 140, adhesive 156 and connection joint 158. Moreparticularly, encapsulant 160 contacts surface 112 and the outer edgesof chip 110, but is spaced and separated from surface 114 of chip 110(due to adhesive 156).

Encapsulant 160 is a solid adherent compressible protective layer thatprovides environmental protection such as moisture resistance andparticle protection for chip 110 as well as mechanical support forrouting line 130 and metal pillar 140. Furthermore, chip 110 and metalpillar 140 are embedded in encapsulant 160.

Encapsulant 160 includes opposing surfaces 162 and 164. Surface 162faces upwardly, and surface 164 faces downwardly. Encapsulant 160extends upwardly beyond chip 110, metal base 120, routing line 130,solder mask 136, metal pillar 140, adhesive 156 and connection joint158, has a thickness of 600 microns and extends 100 microns upwardlybeyond metal pillar 140.

FIGS. 12A, 12B and 12C are cross-sectional, top and bottom views,respectively, of the structure after metal base 120 is removed.

Metal base 120 is removed by applying a blanket back-side wet chemicaletch. For instance, a bottom spray nozzle (not shown) can spray a wetchemical etch on metal base 120 while a top spray nozzle (not shown) isdeactivated, or alternatively, the structure can be dipped in the wetchemical. The wet chemical etch is highly selective of copper withrespect to nickel, polyimide, the solder mask material and the moldingcompound, and therefore, highly selective of metal base 120 with respectto the first nickel layer of routing line 130, solder mask 136, adhesive156 and encapsulant 160. Chip 110, metal pillar 140 and connection joint158 are not exposed to the wet chemical etch. Furthermore, the firstnickel layer of routing line 130, solder mask 136 and encapsulant 160protect the copper layer of routing line 130 from the wet chemical etch.Therefore, no appreciable amount of routing line 130, solder mask 136,adhesive 156 or encapsulant 160 is removed.

The wet chemical etch removes metal base 120. As a result, the wetchemical etch eliminates contact area between metal base 120 and routingline 130 and exposes routing line 130.

A suitable wet chemical etch can be provided by a solution containingalkaline ammonia. The optimal etch time for removing metal base 120without excessively exposing routing line 130 to the wet chemical etchcan be established through trial and error.

Advantageously, encapsulant 160 provides mechanical support for routingline 130 and metal pillar 140 and reduces mechanical strain on soldermask 136 and adhesive 156, which is particularly useful after metal base120 is removed. Encapsulant 160 protects routing line 130 and metalpillar 140 from mechanical damage by the wet chemical etch andsubsequent cleaning steps (such as rinsing in distilled water and airblowing). For instance, encapsulant 160 absorbs physical force of thewet chemical etch and cleaning steps that might otherwise separaterouting line 130 from metal pillar 140. Thus, encapsulant 160 improvesstructural integrity and allows the wet chemical etch and subsequentcleaning steps to be applied more vigorously, thereby improvingmanufacturing throughput.

FIGS. 13A, 13B and 13C are cross-sectional, top and bottom views,respectively, of insulative base 166 formed on routing line 130, soldermask 136, adhesive 156 and encapsulant 160.

Insulative base 166 is initially an epoxy in paste form that includes anepoxy resin, a curing agent, an accelerator and a filler. The filler isan inert material, such as silica (powdered fused quartz), that improvesthermal conductivity, thermal shock resistance, and thermal coefficientof expansion matching. The epoxy paste is blanketly deposited on routingline 130, solder mask 136, adhesive 156 and encapsulant 160, and thenthe epoxy paste is cured or hardened at a relatively low temperature inthe range of 100 to 250° C. to form a solid adherent insulator thatprovides a protective seal for routing line 130.

Insulative base 166 contacts and covers and extends downwardly beyondrouting line 130, solder mask 136, adhesive 156 and encapsulant 160,covers and extends downwardly beyond and is spaced from chip 110, metalpillar 140 and connection joint 158, and has a thickness of 50 microns.

For convenience of illustration, insulative base 166 is shown below chip110 to retain a single orientation throughout the figures for ease ofcomparison between the figures, although in this step the structurewould be inverted so that gravitational force would assist the epoxypaste deposition.

FIGS. 14A, 14B and 14C are cross-sectional, top and bottom views,respectively, of the structure after an upper portion of encapsulant 160is removed.

The upper portion of encapsulant 160 is removed by grinding. Inparticular, a rotating diamond sand wheel and distilled water areapplied to surface 162 of encapsulant 160. Initially, the diamond sandwheel grinds only encapsulant 160. As the grinding continues,encapsulant 160 becomes thinner as surface 162 migrates downwardly.Eventually the diamond sand wheel contacts stem 152, and as a result,begins to grind stem 152 as well. As the grinding continues, stem 152and encapsulant 160 become thinner as their grinded surfaces migratedownwardly. The grinding continues until stem 152 and encapsulant 160have the desired thickness, and then halts before it reaches chip 110,routing line 130, solder mask 136, ball bond 150, adhesive 156,connection joint 158 or insulative base 166. Thereafter, the structureis rinsed in distilled water to remove contaminants.

Metal pillar 140 and encapsulant 160 extend upwardly beyond chip 110 by250 microns after the grinding operation. Thus, the grinding removes a100 micron thick upper portion of metal pillar 140 and a 200 micronthick upper portion of encapsulant 160. Furthermore, the grindingexposes distal end 168 of stem 152 that faces away from ball bond 150and is laterally aligned with surface 162 of encapsulant 160. Thus,metal pillar 140 remains welded to routing line 130 and stem 152 remainsan elongated straight wire segment with a uniform diameter that extendsvertically farther than ball bond 150 but is shortened.

At this stage, chip 110 and metal pillar 140 remain embedded inencapsulant 160. Metal pillar 140 and surface 162 of encapsulant 160 arelaterally aligned with one another and exposed. Thus, an exposedplanarized horizontal surface that faces upwardly includes metal pillar140 and encapsulant 160. Metal pillar 140 and encapsulant 160 continueto extend upwardly beyond chip 110, routing line 130, solder mask 136,adhesive 156, connection joint 158 and insulative base 166, metal pillar140 continues to extend vertically across most of the thickness of chip110, and encapsulant 160 continues to cover chip 110. Furthermore, metalpillar 140 extends through surface 162 of encapsulant 160, andencapsulant 160 no longer covers metal pillar 140. Stated differently,metal pillar 140 is not covered in the upward direction by encapsulant160 or any other insulative material of the structure.

FIGS. 15A, 15B and 15C are cross-sectional, top and bottom views,respectively, of plated contact terminal 170 formed on metal pillar 140.

Plated contact terminal 170 includes convex surface 172 and flat surface174. Convex surface 172 is spaced from metal pillar 140 and encapsulant160 and includes apex 176 that faces away from metal pillar 140 andencapsulant 160, and flat surface 174 contacts and faces towards metalpillar 140 and encapsulant 160.

Plated contact terminal 170 has a hemispherical shape with a height(between flat surface 174 and apex 176) of 75 microns and a diameter (atflat surface 174) of 150 microns that decreases as the height increases(away from flat surface 174 towards apex 176). In addition, platedcontact terminal 170 is vertically aligned with metal pillar 140. As aresult, plated contact terminal 170 covers metal pillar 140, and thusball bond 150, stem 152 and distal end 168 are disposed within theperiphery of plated contact terminal 170. Furthermore, plated contactterminal 170 has a diameter (150 microns) that is two and one-half timesas large as the diameter (60 microns) of ball bond 150 and six times aslarge as the diameter (25 microns) of stem 152 and distal end 168.

Plated contact terminal 170 is electrolessly plated on and only ondistal end 168, and contacts only encapsulant 160 and distal end 168. Asa result, routing line 130 and plated contact terminal 170 are the onlyelectrical conductors that contact metal pillar 140, and routing line130, encapsulant 160 and plated contact terminal 170 are the onlymaterials that contact metal pillar 140.

The structure is submerged in an electroless copper plating solutionsuch as Shipley CUPOSIT™ 250 at 60° C. Metal pillar 140 is gold andtherefore is catalytic to electroless copper. Furthermore, encapsulant160 and insulative base 166 are not catalytic to electroless copper andtherefore a plating mask is not necessary. As a result, plated contactterminal 170 electrolessly plates on and only on distal end 168 and hasa dome-like shape that vertically and laterally expands as theelectroless copper plating operation occurs.

The electroless copper plating operation continues until plated contactterminal 170 has the desired dimensions. Thereafter, the structure isremoved from the electroless copper plating solution and rinsed indistilled water.

Plated contact terminal 170 contacts and is electrically connected tometal pillar 140 at distal end 168 and extends upwardly beyond metalpillar 140 and encapsulant 160. Thus, plated contact terminal 170provides a robust, permanent electrical connection to metal pillar 140.Furthermore, since plated contact terminal 170 has a much largerdiameter than distal end 168, plated contact terminal 170 provides anenlarged contact terminal for metal pillar 140.

At this stage, conductive trace 154 includes routing line 130, metalpillar 140 and plated contact terminal 170 and is electrically connectedto pad 116 by connection joint 158.

FIGS. 16A, 16B and 16C are cross-sectional, top and bottom views,respectively, of opening 178 that extends through insulative base 166and exposes routing line 130.

Opening 178 is formed through insulative base 166 by applying a suitableetch that is highly selective of insulative base 166 with respect torouting line 130. In this instance, a selective TEA CO₂ laser etch isapplied using multiple laser direct writes. The laser is directed atenlarged circular portion 134 of routing line 130. The laser has a spotsize of 150 microns, and enlarged circular portion 134 has a diameter of400 microns. Furthermore, the laser direct writes are offset relative toone another yet overlap so that the laser scans a central portion ofenlarged circular portion 134 with a diameter of 300 microns. In thismanner, the laser direct writes in combination are vertically alignedwith and centered relative to enlarged circular portion 134. As aresult, the laser strikes routing line 130, a portion of insulative base166 that extends within the periphery of routing line 130, and ablatesinsulative base 166.

The laser drills through and removes a portion of insulative base 166.However, a portion of insulative base 166 that extends across theperipheral edges of enlarged circular portion 134 is outside the scopeof the laser and remains intact.

Thereafter, a brief cleaning step can be applied to remove oxides anddebris that may be present on the exposed portion of routing line 130.For instance, a brief oxygen plasma cleaning step can be applied to thestructure. Alternatively, a brief wet chemical cleaning step using asolution containing potassium permanganate can be applied to thestructure. In either case, the cleaning step cleans the exposed portionof routing line 130 without damaging the structure. Likewise, thecleaning step can clean plated contact terminal 170.

Opening 178 is formed in and extends vertically through insulative base166, is disposed outside the periphery of chip 110, is verticallyaligned with and exposes enlarged circular portion 134 of routing line130, is spaced from elongated routing portion 132 of routing line 130,adhesive 156 and encapsulant 160 and has a diameter of 300 microns.Opening 178 is formed without damaging routing line 130 or metal pillar140 and does not extend into encapsulant 160.

Opening 178 may have a diameter that is slightly larger than 300 micronsdue to the beam angle of the laser, the thermal effects of the laser,and/or the isotropic nature of an oxygen plasma or wet chemical cleaningstep. For convenience of explanation, this slight enlargement isignored.

As a result, insulative base 166 contains opening 178 with a diameter of300 microns that is vertically aligned with and selectively exposesenlarged circular portion 134. Insulative base 166 exposes an innercircular region of enlarged circular portion 134 with a diameter of 300microns, and covers an outer annular region of enlarged circular portion134 with a width of 50 microns ((400−300)/2). In addition, openings 138and 178 are vertically aligned with one another.

FIGS. 17A, 17B and 17C are cross-sectional, top and bottom views,respectively, of plated terminal 180 formed on routing line 130.

Plated terminal 180 is electrolessly plated on the exposed portion ofrouting line 130. More particularly, plated terminal 180 is plated onenlarged circular portion 134 of routing line 130 in opening 178.

Plated terminal 180 is composed of a nickel layer electrolessly platedon routing line 130 and a gold layer electrolessly plated on the nickellayer. In plated terminal 180, the nickel layer contacts and issandwiched between routing line 130 and the gold layer, and the goldlayer is spaced and separated from routing line 130 and exposed. Forconvenience of illustration, the nickel and gold layers are shown as asingle layer.

Initially, the structure is submerged in an electroless nickel platingsolution such as Enthone Enplate NI-424 at 85° C. Preferred nickelplating solutions include nickel-sulfate and nickel-chloride and have apH of about 9.5 to 10.5. A higher nickel concentration provides a fasterplating rate but reduces the stability of the solution. The amount ofchelating agents or ligands in the solution depends on the nickelconcentration and their chemical structure, functionality and equivalentweight. Most of the chelating agents used in electroless nickel platingsolutions are hydroxy organic acids which form one or more water solublenickel ring complexes. These complexes reduce the free nickel ionconcentration, thereby increasing the stability of the solution whileretaining a reasonably fast plating rate. Generally, the higher thecomplex agent concentration, the slower the plating rate. In addition,the pH of the solution and the plating rate continually decrease as theelectroless plating continues due to hydrogen ions being introduced intothe solution as a byproduct of the nickel reduction. Accordingly, thesolution is buffered to offset the effects of the hydrogen ions.Suitable buffering agents include sodium or potassium salts of mono anddibasic organic acids. Finally, those skilled in the art will understandthat electroless nickel plating solutions do not deposit pure elementalnickel since a reducing agent such as H₂PO₂ will naturally decomposeinto the electrolessly plated nickel. Therefore, those skilled in theart will understand that electrolessly plated nickel refers to a nickelcompound that is mostly nickel but not pure elemental nickel.

Routing line 130 includes an exposed nickel surface layer and thereforeis catalytic to electroless nickel. Furthermore, encapsulant 160 andinsulative base 166 are not catalytic to electroless nickel andtherefore a plating mask is not necessary. As a result, plated terminal180 plates on routing line 130.

The electroless nickel plating operation continues until plated terminal180 is about 4 microns thick. At this point, plated terminal 180 isprimarily nickel and contains about 4 to 9 weight percentage phosphorus.

Thereafter, the structure is removed from the electroless nickel platingsolution and briefly submerged in an electroless gold plating solutionsuch as is MacDermid PLANAR™ at 70° C. Plated terminal 180 includes anexposed nickel surface layer and therefore is catalytic to electrolessgold. Furthermore, encapsulant 160 and insulative base 166 are notcatalytic to electroless gold and therefore a plating mask is notnecessary. As a result, the gold deposits on the nickel surface layer.The gold electroless plating operation continues until the gold surfacelayer is about 0.5 microns thick. Thereafter, the structure is removedfrom the electroless gold plating solution and rinsed in distilledwater.

Plated terminal 180 contacts and is electrically connected to routingline 130 in opening 178 and extends downwardly beyond routing line 130.Plated terminal 180 contacts and covers the portion of routing line 130that was previously exposed by opening 178. Thus, plated terminal 180provides a robust, permanent electrical connection to routing line 130that protrudes downwardly from routing line 130 and is exposed. Platedterminal 180 includes a buried nickel layer and a gold surface layer.The buried nickel layer provides the primary mechanical and electricalconnection to routing line 130, and the gold surface layer provides awettable surface to facilitate solder reflow. Plated terminal 180 has acylindrical shape with a diameter of 300 microns.

Plated contact terminal 170 is also exposed to the electroless nickelplating solution and then the electroless gold plating solution. Platedcontact terminal 170 is copper and therefore is not catalytic toelectroless nickel. However, plated contact terminal 170 is electricallyconnected to routing line 130 by metal pillar 140, and plated terminal180 changes the electrochemical potential of routing line 130, metalpillar 140 and plated contact terminal 170 by a small amount such as 0.2volts. As a result, plated contact terminal 170 becomes catalytic toelectroless nickel, and nickel and gold layers electrolessly plate onplated contact terminal 170 as well.

Plated contact terminal 170 expands slightly beyond the copper layer andincludes a buried copper layer, a buried nickel layer and a gold surfacelayer. The buried copper layer (formed during the electroless copperplating operation) contacts the buried nickel layer and is spaced fromthe gold surface layer, the buried nickel layer contacts and issandwiched between the buried copper layer and the gold surface layer,and the gold surface layer is exposed and provides a wettable surface tofacilitate solder reflow as well as a weldable surface to facilitate awedge bond. For convenience of illustration, the copper, nickel and goldlayers are shown as a single layer.

At this stage, conductive trace 154 includes routing line 130, metalpillar 140, plated contact terminal 170 and plated terminal 180 and iselectrically connected to pad 116 by connection joint 158. Connectionjoint 158, plated contact terminal 170 and plated terminal 180 arespaced and separated from one another, and plated contact terminal 170and plated terminal 180 are vertically aligned with one another.

FIGS. 18A, 18B and 18C are cross-sectional, top and bottom views,respectively, of solder terminal 182 formed on plated terminal 180.

Solder terminal 182 is initially a tin-lead ball with a spherical shape.The tin-lead ball is dipped in flux to provide solder terminal 182 witha flux surface coating that surrounds the tin-lead ball. Thereafter, thestructure is inverted so that plated terminal 180 faces upwardly, andsolder terminal 182 is deposited on plated terminal 180. Solder terminal182 weakly adheres to plated terminal 180 due to the flux surfacecoating of solder terminal 182.

Thereafter, heat is applied to reflow solder terminal 182. Platedterminal 180 contains a gold surface layer that provides a wettablesurface for solder reflow. As a result, solder terminal 182 wets platedterminal 180. The heat is then removed and solder terminal 182 cools andsolidifies, and contacts a larger surface area of and remains proximateto plated terminal 180.

Solder terminal 182 contacts and is electrically connected to platedterminal 180 and extends downwardly beyond insulative base 166 andplated terminal 180. Thus, solder terminal 182 provides a reflowableelectrical connection to plated terminal 180 that protrudes downwardlyfrom insulative base 166 and plated terminal 180 and is exposed. Solderterminal 182 has a substantially hemispherical shape with a diameter ofabout 300 microns.

At this stage, conductive trace 154 includes routing line 130, metalpillar 140, plated contact terminal 170, plated terminal 180 and solderterminal 182. Plated contact terminal 170 and solder terminal 182 arevertically aligned with one another and provide contact terminals forthe assembly.

FIGS. 19A, 19B and 19C are cross-sectional, top and bottom views,respectively, of the structure after cutting encapsulant 160 andinsulative base 166 with an excise blade to singulate the assembly fromother assemblies.

At this stage, the manufacture of semiconductor chip assembly 198 thatincludes chip 110, routing line 130, solder mask 136, metal pillar 140,adhesive 156, connection joint 158, encapsulant 160, insulative base166, plated contact terminal 170, plated terminal 180 and solderterminal 182 can be considered complete.

Routing line 130 is mechanically coupled to chip 110 by adhesive 156 andencapsulant 160, and is electrically coupled to chip 110 by connectionjoint 158. Routing line 130 provides horizontal fan-out routing betweenpad 116 and external circuitry, and metal pillar 140 provides verticalrouting between pad 116 and external circuitry. Metal pillar 140 extendsvertically across most of the thickness of chip 110, is welded to andonly to routing line 130, is not covered in the upward direction byencapsulant 160 or any other insulative material of the assembly, and isnot covered in the downward direction by insulative base 166 or anyother insulative material of the assembly. Encapsulant 160 andinsulative base 166 provide mechanical support and environmentalprotection for the assembly. Encapsulant 160 has most of surface 162exposed in the upward direction, and surface 164 is covered in thedownward direction.

The semiconductor chip assembly is a single-chip first-level package.Thus, chip 110 is the only chip embedded in encapsulant 160.

The semiconductor chip assembly includes other conductive tracesembedded in encapsulant 160, and only a single conductive trace 154 isshown for convenience of illustration. The conductive traces are spacedand separated and electrically isolated from one another. The conductivetraces each include a respective routing line, metal pillar, platedcontact terminal, plated terminal and solder terminal. The conductivetraces are each electrically connected to a respective pad on chip 110by a respective connection joint. The conductive traces each extendbeyond an outer edge of chip 110 and extend across most of the thicknessof chip 110 to provide horizontal fan-out routing and vertical routingfor their respective pads. Furthermore, the conductive traces eachinclude an upwardly protruding plated contact terminal and a downwardlyprotruding solder terminal to facilitate a three-dimensional stackedarrangement.

Chip 110 is designed with the pads electrically isolated from oneanother. However, the corresponding routing lines are initiallyelectroplated on metal base 120 and electrically connected to oneanother by metal base 120. Furthermore, the connection jointselectrically connect the routing lines and the corresponding pads,thereby electrically connecting the pads with one another. Thereafter,once metal base 120 is etched and removed, the routing lines areelectrically isolated from one another, and therefore, the pads returnto being electrically isolated from one another.

Advantageously, there is no plating bus or related circuitry that needbe disconnected or severed from the conductive traces after the metalbase is removed.

FIGS. 20A, 20B and 20C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with asecond embodiment of the present invention. In the second embodiment,the chip is flip-chip bonded. For purposes of brevity, any descriptionin the first embodiment is incorporated herein insofar as the same isapplicable, and the same description need not be repeated. Likewise,elements of the second embodiment similar to those in the firstembodiment have corresponding reference numerals indexed at two-hundredrather than one-hundred. For instance, chip 210 corresponds to chip 110,routing line 230 corresponds to routing line 130, etc.

Connection joint 258 is initially a solder bump deposited on pad 216.The solder bump has a hemispherical shape and a diameter of 100 microns.

Routing line 230 extends within and outside the periphery of chip 210and is disposed downwardly beyond chip 210. Thus, the elongated routingportion (corresponding to elongated routing portion 132) is lengthened.This is accomplished by a slight adjustment to the electroplatingoperation previously described for routing line 130. In particular, thephotoresist layer (corresponding to photoresist layer 126) is patternedto reshape the opening for the routing line 230, and therefore routingline 230 is lengthened relative to routing line 130.

Solder mask 236 extends laterally beyond routing line 230 in thedirection away from metal pillar 240, and includes opening 279 thatselectively exposes a portion of routing line 230 near the distal end ofrouting line 230 opposite metal pillar 240.

Chip 210 is positioned such that surface 212 faces downwardly, surface214 faces upwardly, routing line 230 extends laterally across pad 216,and connection joint 258 is aligned with and extends into opening 279and contacts and is sandwiched between pad 216 and routing line 230.Furthermore, metal pillar 240 extends vertically across all of thethickness of chip 210. Thereafter, heat is applied to reflow connectionjoint 258, and then the heat is removed and connection joint 258 coolsand solidifies into a hardened solder joint that mechanically attachesand electrically connects pad 216 and routing line 230. Furthermore,connection joint 258 exhibits localized wetting and does not collapse,and chip 210 remains spaced and separated from routing line 230 andsolder mask 236.

Thereafter, adhesive 256 is dispensed into and underfills the open gapbetween chip 210 and solder mask 236, and then adhesive 256 is cured. Asa result, adhesive 256 contacts and is sandwiched between chip 210 andsolder mask 236, contacts connection joint 258 and is spaced andseparated from pad 216. Thus, adhesive 256 is significantly thicker thanadhesive 156. A suitable underfill adhesive is Namics U8443.

Thereafter, encapsulant 260, insulative base 266, plated contactterminal 270, plated terminal 280 and solder terminal 282 are formed.

Semiconductor chip assembly 298 includes chip 210, routing line 230,solder mask 236, metal pillar 240, adhesive 256, connection joint 258,encapsulant 260, insulative base 266, plated contact terminal 270,plated terminal 280 and solder terminal 282.

FIGS. 21A, 21B and 21C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with athird embodiment of the present invention. In the third embodiment, theconnection joint is electroplated. For purposes of brevity, anydescription in the first embodiment is incorporated herein insofar asthe same is applicable, and the same description need not be repeated.Likewise, elements of the third embodiment similar to those in the firstembodiment have corresponding reference numerals indexed atthree-hundred rather than one-hundred. For instance, chip 310corresponds to chip 110, routing line 330 corresponds to routing line130, etc.

Pad 316 is treated to accommodate an electroplated copper connectionjoint by forming a nickel surface layer on the aluminum base. Forinstance, chip 310 is dipped in a zinc solution to deposit a zinc layeron the aluminum base. This step is commonly known as zincation.Preferably, the zinc solution contains about 150 grams/liter of NaOH, 25grams/liter of ZnO, and 1 gram/liter of NaNO₃, as well as tartaric acidto reduce the rate at which the aluminum base dissolves. Thereafter, thenickel surface layer is electrolessly deposited on the zincated aluminumbase. A suitable electroless nickel plating solution is Enthone EnplateNI-424 at 85° C.

Routing line 330 extends within and outside the periphery of chip 310and is disposed downwardly beyond chip 310. Thus, the elongated routingportion (corresponding to elongated routing portion 132) is lengthened.This is accomplished by a slight adjustment to the electroplatingoperation previously described for routing line 130. In particular, thephotoresist layer (corresponding to photoresist layer 126) is patternedto reshape the opening for the routing line 330, and therefore routingline 330 is lengthened relative to routing line 130.

The metal base (corresponding to metal base 120) is etched on the sideopposite routing line 330 to form a recess (not shown), and thenadhesive 356 is deposited on the metal base and routing line 330.

Chip 310 is inverted and positioned such that surface 312 facesdownwardly, surface 314 faces upwardly, adhesive 356 contacts and issandwiched between pad 316 and routing line 330, and routing line 330partially overlaps pad 316. Furthermore, metal pillar 340 extendsvertically across all of the thickness of chip 310. Thereafter,encapsulant 360 is formed, and then the metal base is etched again toconvert the recess into a slot (not shown) that extends through themetal base, exposes adhesive 356 and is vertically aligned with pad 316.

Thereafter, through-hole 381 is formed in adhesive 356 that exposes pad316. Through-hole 381 is formed by applying a suitable etch that ishighly selective of adhesive 356 with respect to pad 316 and routingline 330. In this instance, a selective TEA CO₂ laser etch is applied.The laser is directed at and vertically aligned with and centeredrelative to pad 316. The laser has a spot size of 70 microns, and pad316 has a length and width of 100 microns. As a result, the laserstrikes pad 316 and portions of routing line 330 and adhesive 356 thatextend within the periphery of pad 316, and ablates adhesive 356. Thelaser drills through and removes a portion of adhesive 356. However,portions of adhesive 356 that extend across the peripheral edges of pad316 are outside the scope of the laser and remain intact. Likewise,routing line 330 shields a portion of adhesive 356 from the laser etch,and a portion of adhesive 356 sandwiched between pad 316 and routingline 330 remains intact. The laser etch is anisotropic, and thereforelittle or none of adhesive 356 sandwiched between pad 316 and routingline 330 is undercut or removed. Through-hole 381 may slightly undercutadhesive 356 between pad 316 and routing line 330 and have a diameterthat is slightly larger than 70 microns due to the beam angle of thelaser, the thermal effects of the laser, and/or the isotropic nature ofan oxygen plasma or wet chemical cleaning step. For convenience ofexplanation, this slight undercut and enlargement is ignored. However,through-hole 381 is formed without damaging chip 310 or routing line 330and does not extend into chip 310.

Thereafter, a brief cleaning step can be applied to remove oxides anddebris that may be present on the exposed portions of pad 316 androuting line 330. For instance, a brief oxygen plasma cleaning step canbe applied to the structure. Alternatively, a brief wet chemicalcleaning step using a solution containing potassium permanganate can beapplied to the structure. In either case, the cleaning step cleans theexposed portions of pad 316 and routing line 330 without damaging thestructure.

Thereafter, connection joint 358 is formed by an electroplatingoperation. Initially, the metal base is connected to a plating bus (notshown), current is applied to the plating bus from an external powersource, and the structure is submerged in an electrolytic copper platingsolution such as Sel-Rex CUBATH M™ at room temperature. As a result,connection joint 358 electroplates on the exposed portions of the metalbase. In addition, since the plating bus provides the current to themetal base, which in turn provides the current to routing line 330,connection joint 358 electroplates on the exposed portions of routingline 330 in through-hole 381. At the initial stage, since adhesive 356is an electrical insulator and pad 316 is not connected to the platingbus, connection joint 358 does not electroplate on pad 316 and is spacedfrom pad 316. However, as the copper electroplating continues,connection joint 358 continues to plate on routing line 330, extendsthrough adhesive 356 and contacts pad 316. As a result, pad 316 isconnected to the plating bus by the metal base, routing line 330 andconnection joint 358, and therefore connection joint 358 begins toelectroplate on pad 316 as well. The copper electroplating continuesuntil connection joint 358 has the desired thickness. Thereafter, thestructure is removed from the electrolytic copper plating solution andrinsed in distilled water to remove contaminants.

Thereafter, insulative plug 383 is formed on adhesive 356 and connectionjoint 358 and disposed within the slot, then the metal base is etchedand removed, then insulative base 366 is formed, then metal pillar 340and encapsulant 360 are grinded, and then plated contact terminal 370,plated terminal 380 and solder terminal 382 are formed.

Semiconductor chip assembly 398 includes chip 310, routing line 330,solder mask 336, metal pillar 340, adhesive 356, connection joint 358,encapsulant 360, insulative base 366, plated contact terminal 370,plated terminal 380, solder terminal 382 and insulative plug 383.

FIGS. 22A, 22B and 22C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with afourth embodiment of the present invention. In the fourth embodiment,the connection joint is electrolessly plated. For purposes of brevity,any description in the first embodiment is incorporated herein insofaras the same is applicable, and the same description need not berepeated. Likewise, elements of the fourth embodiment similar to thosein the first embodiment have corresponding reference numerals indexed atfour-hundred rather than one-hundred. For instance, chip 410 correspondsto chip 110, routing line 430 corresponds to routing line 130, etc.

Pad 416 is treated to include a nickel surface layer in the same manneras pad 316, routing line 430 is configured in the same manner as routingline 330, and adhesive 456 is deposited on the metal base (correspondingto metal base 120) and routing line 430 in the same manner that adhesive356 is deposited on the metal base and routing line 330.

Chip 410 is inverted and positioned such that surface 412 facesdownwardly, surface 414 faces upwardly, adhesive 456 contacts and issandwiched between pad 416 and routing line 430, and routing line 430partially overlaps pad 416. Furthermore, metal pillar 440 extendsvertically across all of the thickness of chip 410. Thereafter,encapsulant 460 is formed, and then the metal base is etched andremoved, thereby exposing adhesive 456. Thereafter, through-hole 481 isformed in adhesive 456 and exposes pad 416. Through-hole 481 is formedin the same manner as through-hole 381.

Thereafter, connection joint 458 is formed by an electroless platingoperation. The structure is submerged in an electroless nickel platingsolution such as Enthone Enplate NI-424 at 85° C. Pad 416 includes anexposed nickel surface layer and therefore is catalytic to electrolessnickel. Connection joint 458 plates on pad 416 and eventually contactsand electrically connects pad 416 and routing line 430 in through-hole481. The electroless nickel plating operation continues until connectionjoint 458 is about 10 microns thick. Thereafter, the structure isremoved from the electroless nickel plating solution and rinsed indistilled water.

Thereafter, insulative base 466 is formed, then metal pillar 440 andencapsulant 460 are grinded, and then plated contact terminal 470,plated terminal 480 and solder terminal 482 are formed.

Semiconductor chip assembly 498 includes chip 410, routing line 430,solder mask 436, metal pillar 440, adhesive 456, connection joint 458,encapsulant 460, insulative base 466, plated contact terminal 470,plated terminal 480 and solder terminal 482.

FIGS. 23A, 23B and 23C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with afifth embodiment of the present invention. In the fifth embodiment, theball bond extends across most of the thickness of the chip. For purposesof brevity, any description in the first embodiment is incorporatedherein insofar as the same is applicable, and the same description neednot be repeated. Likewise, elements of the fifth embodiment similar tothose in the first embodiment have corresponding reference numeralsindexed at five-hundred rather than one-hundred. For instance, chip 510corresponds to chip 110, routing line 530 corresponds to routing line130, etc.

Metal pillar 540 is formed from a gold wire with a diameter of 50microns (rather than 25 microns) and a wire ball with a diameter of 125microns (rather than 60 microns). As a result, ball bond 550 has aheight of 100 microns and a diameter of 150 microns, and stem 552 has adiameter of 50 microns. Furthermore, ball bond 550 (rather than stem552) extends across most of the thickness of chip 510.

Semiconductor chip assembly 598 includes chip 510, routing line 530,solder mask 536, metal pillar 540, adhesive 556, connection joint 558,encapsulant 560, insulative base 566, plated contact terminal 570,plated terminal 580 and solder terminal 582.

FIGS. 24A, 24B and 24C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with asixth embodiment of the present invention. In the sixth embodiment, theplated contact terminal is electroplated. For purposes of brevity, anydescription in the first embodiment is incorporated herein insofar asthe same is applicable, and the same description need not be repeated.Likewise, elements of the sixth embodiment similar to those in the firstembodiment have corresponding reference numerals indexed at six-hundredrather than one-hundred. For instance, chip 610 corresponds to chip 110,routing line 630 corresponds to routing line 130, etc.

Plated contact terminal 670 is formed by an electroplating operationafter metal pillar 640 and encapsulant 660 are grinded and before themetal base (corresponding to metal base 120) is removed.

Initially, a back-side protective mask such as a polyimide tape isplaced over and covers the bottom surface (corresponding to surface 124)of the metal base, the metal base is connected to a plating bus (notshown), current is applied to the plating bus from an external powersource, and the structure is submerged in an electrolytic copper platingsolution such as Sel-Rex CUBATH M™ at room temperature. As a result,plated contact terminal 670 electroplates on distal end 668 of metalpillar 640. In addition, since the plating bus provides the current tothe metal base, which in turn provides the current to routing line 630,which in turn provides the current to metal pillar 640, the metal base,routing line 630 and metal pillar 640 serve as a plating bus. The copperelectroplating operation continues until the copper layer has thedesired thickness. Thereafter, the structure is removed from theelectrolytic copper plating solution and submerged in an electrolyticnickel plating solution such as Technic Techni Nickel “S” at roomtemperature. As a result, a nickel layer electroplates on the copperlayer. The nickel electroplating operation continues until the nickellayer has the desired thickness. Thereafter, the structure is removedfrom the electrolytic nickel plating solution and submerged in anelectrolytic gold plating solution such as Technic Orotemp at roomtemperature. As a result, a gold layer electroplates on the nickellayer. The gold electroplating operation continues until the gold layerhas the desired thickness. Thereafter, the structure is removed from theelectrolytic gold plating solution and rinsed in distilled water toremove contaminants.

Plated contact terminal 670 has similar size, shape and composition asplated contact terminal 170 but is formed by electroplating (rather thanelectroless plating).

Thereafter, the back-side protective mask is peeled-off and removed,then the metal base is etched and removed, then insulative base 666 isformed, then metal pillar 640 and encapsulant 660 are grinded, then afront-side protective mask is placed on plated contact terminal 670,then plated terminal 680 and solder terminal 682 are formed, and thenthe front-side protective mask is peeled-off and removed.

Semiconductor chip assembly 698 includes chip 610, routing line 630,solder mask 636, metal pillar 640, adhesive 656, connection joint 658,encapsulant 660, insulative base 666, plated contact terminal 670,plated terminal 680 and solder terminal 682.

FIGS. 25A, 25B and 25C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with aseventh embodiment of the present invention. In the seventh embodiment,the encapsulant is blanketly etched to expose the metal pillar. Forpurposes of brevity, any description in the first embodiment isincorporated herein insofar as the same is applicable, and the samedescription need not be repeated. Likewise, elements of the seventhembodiment similar to those in the first embodiment have correspondingreference numerals indexed at seven-hundred rather than one-hundred. Forinstance, chip 710 corresponds to chip 110, routing line 730 correspondsto routing line 130, etc.

Encapsulant 760 is initially an epoxy in paste form that includes anepoxy resin, a curing agent and an accelerator. The epoxy paste isdeposited over the structure using stencil printing, then the epoxypaste is cured or hardened at a relatively low temperature in the rangeof 100 to 250° C. to form a solid adherent insulator. Encapsulant 760extends vertically beyond metal pillar 740 by 20 microns. Furthermore,encapsulant 760 is more susceptible to plasma etching than encapsulant160 since encapsulant 760 is composed of epoxy without a filler whereasencapsulant 160 is composed of molding compound with a filler.

Thereafter, instead of removing the upper portion of encapsulant 760 bygrinding, the upper portion of encapsulant 760 is removed by plasmaetching. The plasma etch continues until metal pillar 740 is exposed,and then halts before it reaches chip 710, routing line 730 orconnection joint 758.

Semiconductor chip assembly 798 includes chip 710, routing line 730,solder mask 736, metal pillar 740, adhesive 756, connection joint 758,encapsulant 760, insulative base 766, plated contact terminal 770,plated terminal 780 and solder terminal 782.

FIGS. 26A, 26B and 26C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with aneighth embodiment of the present invention. In the eighth embodiment,the chip is exposed. For purposes of brevity, any description in thefirst embodiment is incorporated herein insofar as the same isapplicable, and the same description need not be repeated. Likewise,elements of the eighth embodiment similar to those in the firstembodiment have corresponding reference numerals indexed ateight-hundred rather than one-hundred. For instance, chip 810corresponds to chip 110, routing line 830 corresponds to routing line130, etc.

The assembly is manufactured in the same manner as assembly 298 in thesecond embodiment, except that the grinding is applied longer than inthe second embodiment and removes portions of chip 810, metal pillar 840and encapsulant 860. Initially, the diamond sand wheel grinds onlyencapsulant 860. As the grinding continues, encapsulant 860 becomesthinner as its grinded surface migrates downwardly. Eventually thediamond sand wheel contacts stem 852, and as a result, begins to grindstem 852 as well. As the grinding continues, stem 852 and encapsulant860 become thinner as their grinded surfaces migrate downwardly.However, the grinding does not halt before it reaches chip 810. Instead,the grinding continues and eventually the diamond sand wheel contactschip 810, and as a result, begins to grind chip 810 as well. As thegrinding continues, chip 810, stem 852 and encapsulant 860 becomethinner as their grinded surfaces migrate downwardly. The grindingcontinues until chip 810, stem 852 and encapsulant 860 have the desiredthickness, and then halts before it reaches active circuitry in chip810, routing line 830, solder mask 836, ball bond 850 or adhesive 856.Thereafter, the structure is rinsed in distilled water to removecontaminants.

The grinding removes a 50 micron thick upper portion of chip 810 (at theback-side of the inverted chip 810), a 300 micron thick upper portion ofmetal pillar 840 and a 400 micron thick upper portion of encapsulant860.

Chip 810 and metal pillar 840 remain embedded in encapsulant 860.Surface 814 of chip 810, surface 862 of encapsulant 860 and distal end868 of metal pillar 840 are laterally aligned with one another andexposed. Thus, an exposed planarized horizontal surface that facesupwardly includes surfaces 814 and 862 and distal end 868. Furthermore,encapsulant 860 no longer contacts or covers surface 814 of chip 810.Thus, surface 814 of chip 810 is not covered in the upward direction byanother material of the assembly.

Semiconductor chip assembly 898 includes chip 810, routing line 830,solder mask 836, metal pillar 840, adhesive 856, connection joint 858,encapsulant 860, insulative base 866, plated contact terminal 870,plated terminal 880 and solder terminal 882.

FIGS. 27A, 27B and 27C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with aninth embodiment of the present invention. In the ninth embodiment, thesolder mask extends beneath the chip. For purposes of brevity, anydescription in the first embodiment is incorporated herein insofar asthe same is applicable, and the same description need not be repeated.Likewise, elements of the ninth embodiment similar to those in the firstembodiment have corresponding reference numerals indexed at nine-hundredrather than one-hundred. For instance, chip 910 corresponds to chip 110,routing line 930 corresponds to routing line 130, etc.

Solder mask 936 extends laterally beyond routing line 930 in thedirection away from metal pillar 940, and includes opening 984 thatselectively exposes a portion of routing line 930 near the distal end ofrouting line 930 opposite metal pillar 940. Adhesive 956 contacts and issandwiched between chip 910 and solder mask 936, and connection joint958 extends into opening 984.

Semiconductor chip assembly 998 includes chip 910, routing line 930,solder mask 936, metal pillar 940, adhesive 956, connection joint 958,encapsulant 960, insulative base 966, plated contact terminal 970,plated terminal 980 and solder terminal 982.

FIGS. 28A, 28B and 28C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with atenth embodiment of the present invention. In the tenth embodiment, theplated contact terminal and the solder terminal are laterally offset.For purposes of brevity, any description in the first embodiment isincorporated herein insofar as the same is applicable, and the samedescription need not be repeated. Likewise, elements of the tenthembodiment similar to those in the first embodiment have correspondingreference numerals indexed at one-thousand rather than one-hundred. Forinstance, chip 1010 corresponds to chip 110, routing line 1030corresponds to routing line 130, etc.

Routing line 1030 includes an additional enlarged circular portion (notshown) with a diameter of 400 microns at the side opposite the enlargedcircular portion (corresponding to enlarged circular portion 134). Thisis accomplished by a slight adjustment to the electroplating operationpreviously described for routing line 130. In particular, thephotoresist layer (corresponding to photoresist layer 126) is patternedto reshape the opening for routing line 1030, and therefore routing line1030 includes the additional enlarged circular portion.

Opening 1078 is vertically aligned with the additional enlarged circularportion and is disposed laterally between chip 1010 and metal pillar1040. As a result, plated terminal 1080 and solder terminal 1082 arevertically aligned with opening 1078 and laterally offset from metalpillar 1040 and plated contact terminal 1070.

Semiconductor chip assembly 1098 includes chip 1010, routing line 1030,solder mask 1036, metal pillar 1040, adhesive 1056, connection joint1058, encapsulant 1060, insulative base 1066, plated contact terminal1070, plated terminal 1080 and solder terminal 1082.

FIGS. 29A, 29B and 29C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with aneleventh embodiment of the present invention. In the eleventhembodiment, the solder terminal is omitted. For purposes of brevity, anydescription in the first embodiment is incorporated herein insofar asthe same is applicable, and the same description need not be repeated.Likewise, elements of the eleventh embodiment similar to those in thefirst embodiment have corresponding reference numerals indexed ateleven-hundred rather than one-hundred. For instance, chip 1110corresponds to chip 110, routing line 1130 corresponds to routing line130, etc.

The opening (corresponding to opening 178) in insulative base 1166, theplated terminal (corresponding to plated terminal 180) and the solderterminal (corresponding to solder terminal 182) are omitted. Thus, metalpillar 1140 is covered in the downward direction by insulative base1166.

Semiconductor chip assembly 1198 includes chip 1110, routing line 1130,solder mask 1136, metal pillar 1140, adhesive 1156, connection joint1158, encapsulant 1160, insulative base 1166 and plated contact terminal1170.

FIGS. 30A, 30B and 30C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with atwelfth embodiment of the present invention. In the twelfth embodiment,the conductive trace includes a tapered pillar. For purposes of brevity,any description in the first embodiment is incorporated herein insofaras the same is applicable, and the same description need not berepeated. Likewise, elements of the twelfth embodiment similar to thosein the first embodiment have corresponding reference numerals indexed attwelve-hundred rather than one-hundred. For instance, chip 1210corresponds to chip 110, routing line 1230 corresponds to routing line130, etc.

Tapered pillar 1285 is formed by etching the metal base (correspondingto metal base 120) using an etch mask (not shown) to selectively protectthe metal base. Tapered pillar 1285 is an unetched portion of the metalbase defined by the etch mask that is formed subtractively and contactsrouting line 1230.

The wet chemical etch etches completely through the metal base, therebyeffecting a pattern transfer of the etch mask onto the metal base,removing a portion of the metal base within the periphery of chip 1210without removing another portion of the metal base outside the peripheryof chip 1210, exposing routing line 1230, solder mask 1236 and adhesive1256, reducing but not eliminating contact area between the metal baseand routing line 1230, and reducing and eliminating contact area betweenthe metal base and solder mask 1236 and between the metal base andadhesive 1256. Furthermore, the wet chemical etch electrically isolatesrouting line 1230 from the other routing lines that are initiallyelectroplated on and electrically connected to one another by the metalbase.

The wet chemical etch laterally undercuts the metal base adjacent to theetch mask, causing tapered pillar 1285 to taper inwardly as it extendsdownwardly. A suitable taper is between 45 and slightly less than 90degrees, such as approximately 75 degrees.

The optimal etch time for exposing the metal base to the wet chemicaletch in order to form tapered pillar 1285 with the desired dimensionswithout excessively exposing routing line 1230 to the wet chemical etchcan be established through trial and error.

Tapered pillar 1285 includes opposing surfaces 1286 and 1287 and taperedsidewalls 1288 therebetween. Surface 1286 of tapered pillar 1285constitutes an unetched portion of the top surface (corresponding tosurface 122) of the metal base, and surface 1287 of tapered pillar 1285constitutes an unetched portion of the bottom surface (corresponding tosurface 124) of the metal base. Surface 1286 contacts and faces towardsrouting line 1230 and is spaced from and faces away from the etch mask,and surface 1287 contacts and faces towards the etch mask and is spacedfrom and faces away from routing line 1230. Surfaces 1286 and 1287 areflat and parallel to one another. Tapered sidewalls 1288 are adjacent tosurfaces 1286 and 1287 and slant inwardly towards surface 1287.

Tapered pillar 1285 has a conical shape with a height (between surfaces1286 and 1287) of 200 microns and a diameter that decreases as theheight increases (away from surface 1286 and towards surface 1287).Surface 1286 has a circular shape with a diameter of 300 microns, andsurface 1287 has a circular shape with a diameter of 150 microns. Thus,surface 1286 provides the base of tapered pillar 1285, and surface 1287provides the tip of tapered pillar 1285.

Tapered pillar 1285 contacts routing line 1230, is spaced and separatedfrom metal pillar 1240 and connection joint 1258, is overlapped by andvertically aligned with the enlarged circular portion of routing line1230, metal pillar 1240 and plated contact terminal 1270, is disposedoutside the periphery of chip 1210 and is disposed downwardly beyondchip 1210, routing line 1230, solder mask 1236, metal pillar 1240,adhesive 1256, connection joint 1258, encapsulant 1260 and platedcontact terminal 1270. Routing line 1230 and tapered pillar 1285 contactone another, adhere to one another, are adjacent to one another, and aremetallurgically bonded to one another but are not integral with oneanother and are not metallurgically welded to one another.

Surfaces 1286 and 1287 are vertically aligned with the etch mask, theenlarged circular portion of routing line 1230, metal pillar 1240,plated contact terminal 1270 and one another. In addition, surface 1287is concentrically disposed within the surface areas of surface 1286, theetch mask and the enlarged circular portion of routing line 1230.

Thereafter, the etch mask is removed, then insulative base 1266 isformed with a thickness of 250 microns (rather than 50 microns) andcovers tapered pillar 1285 in the downward direction, then metal pillar1240 and encapsulant 1260 are grinded, then plated contact terminal 1270is formed, and then a lower portion of insulative base 1266 is removedby plasma etching such that tapered pillar 1285 extends downwardlybeyond insulative base 1266 by 150 microns and is exposed.

The opening (corresponding to opening 178) in insulative base 1266, theplated terminal (corresponding to plated terminal 180) and the solderterminal (corresponding to solder terminal 182) are omitted.

Semiconductor chip assembly 1298 includes chip 1210, routing line 1230,solder mask 1236, metal pillar 1240, adhesive 1256, connection joint1258, encapsulant 1260, insulative base 1266, plated contact terminal1270 and tapered pillar 1285.

FIGS. 31A, 31B and 31C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with athirteenth embodiment of the present invention. In the thirteenthembodiment, the routing line is formed on the insulative base and themetal base is omitted. For purposes of brevity, any description in thefirst embodiment is incorporated herein insofar as the same isapplicable, and the same description need not be repeated. Likewise,elements of the thirteenth embodiment similar to those in the firstembodiment have corresponding reference numerals indexed atthirteen-hundred rather than one-hundred. For instance, chip 1310corresponds to chip 110, routing line 1330 corresponds to routing line130, etc.

The metal base (corresponding to metal base 120) is omitted, and thusthe metal base etch and removal are omitted.

Substrate 1389 includes routing line 1330 and insulative base 1366.Substrate 1389 is provided before chip 1310 or metal pillar 1340 isattached to routing line 1330. Routing line 1330 is composed of copper,and insulative base 1366 is composed of insulative glass-reinforced FR-4epoxy. Routing line 1330 includes front-side routing portion 1390,vertical connection 1391 and back-side routing portion 1392. Insulativebase 1366 includes opposing major surfaces 1393 and 1394.

Front-side routing portion 1390 is disposed at surface 1393, back-siderouting portion 1392 is disposed at surface 1394, and verticalconnection 1391 is contiguous with front-side routing portion 1390 atsurface 1393 and back-side routing portion 1392 at surface 1394 andextends through insulative base 1366 to surfaces 1393 and 1394. Thus,routing line 1330 provides horizontal routing at surfaces 1393 and 1394and vertical routing between surfaces 1393 and 1394. In addition,front-side routing portion 1390 is flat and protrudes from insulativebase 1366 at surface 1393, and back-side routing portion 1392 is flatand protrudes from insulative base 1366 at surface 1394.

Front-side routing portion 1390 includes an elongated routing portionwith a width (orthogonal to its elongated length) of 100 microns and anenlarged circular portion with a diameter of 400 microns, back-siderouting portion 1392 includes an elongated routing portion with a width(orthogonal to its elongated length) of 100 microns and an enlargedcircular portion with a diameter of 400 microns, and vertical connection1391 is an enlarged annular region with a diameter of 200 microns.Front-side routing portion 1390 and back-side routing portion 1392 havea thickness of 18 microns, and insulative base 1366 has a thickness of400 microns.

Substrate 1389 is manufactured by providing insulative base 1366,laminating first and second copper layers on surfaces 1393 and 1394,respectively, of insulative base 1366, mechanically drilling athrough-hole through the metal layers and insulative base 1366,performing a plating operation to form a plated through-hole (PTH) thatprovides vertical connection 1391, depositing first and second etchmasks on the first and second metal layers, respectively, providing awet chemical etch that selectively etches an exposed portion of thefirst copper layer through an opening in the first etch mask to formfront-side routing portion 1390 from an unetched portion of the firstmetal layer and that selectively etches an exposed portion of the secondcopper layer through an opening in the second etch mask to formback-side routing portion 1392 from an unetched portion of the secondmetal layer, and then stripping the etch masks.

Solder mask 1336 is formed on front-side routing portion 1390 andsurface 1393 of insulative base 1366 in the same manner that solder mask236 is formed on routing line 230 and the metal base (corresponding tometal base 120), and solder mask 1337 is formed on back-side routingportion 1392 and surface 1394 of insulative base 1366 in the same manneras solder mask 1336. Solder mask 1336 includes an opening (correspondingto opening 138) that exposes the enlarged circular portion of front-siderouting portion 1390 and another opening (corresponding to opening 279)that exposes a portion of front-side routing portion 1390 near thedistal end of front-side routing portion 1390, and likewise, solder mask1337 includes an opening that exposes the enlarged circular portion ofback-side routing portion 1392.

Connection joint 1358 is formed as a solder bump on chip 1310 in thesame manner that connection joint 258 is formed on chip 210. Thereafter,chip 1310 is flip-chip mounted on routing line 1330 such that connectionjoint 1358 contacts and mechanically attaches and electrically connectspad 1316 and routing line 1330 in the same manner that chip 210 isflip-chip mounted on routing line 230, then adhesive 1356 is dispensedinto and underfills the open gap between chip 1310 and solder mask 1336and is cured in the same manner as adhesive 256 is dispensed and cured,then metal pillar 1340 and encapsulant 1360 are formed, then metalpillar 1340 and encapsulant 1360 are grinded, and then plated contactterminal 1370, plated terminal 1380 and solder terminal 1382 are formed.

Semiconductor chip assembly 1398 includes chip 1310, routing line 1330,solder masks 1336 and 1337, metal pillar 1340, adhesive 1356, connectionjoint 1358, encapsulant 1360, insulative base 1366, plated contactterminal 1370, plated terminal 1380 and solder terminal 1382.

FIGS. 32A, 32B and 32C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with afourteenth embodiment of the present invention. In the fourteenthembodiment, the assembly includes a heat sink. For purposes of brevity,any description in the first embodiment is incorporated herein insofaras the same is applicable, and the same description need not berepeated. Likewise, elements of the fourteenth embodiment similar tothose in the first embodiment have corresponding reference numeralsindexed at fourteen-hundred rather than one-hundred. For instance, chip1410 corresponds to chip 110, routing line 1430 corresponds to routingline 130, etc.

Insulative base 1466 is a high thermal conductivity adhesive such asHysol QMI 536HT and has a thickness of 25 microns (rather than 50microns). Heat sink 1495 is a copper plate with a thickness of 150microns.

Insulative base 1466 is initially a liquid resin (A stage) such aspolyamic acid that is deposited on routing line 1430, solder mask 1436,adhesive 1456 and encapsulant 1460 using stencil printing. Thereafter,the structure is placed in an oven and insulative base 1466 is heated toa relatively low temperature such as 100° C. As a result, insulativebase 1466 is partially polymerized (B stage) and forms a gel but is notfully cured. Thereafter, heat sink 1495 is placed on insulative base1466, and insulative base 1466 contacts and is sandwiched betweenrouting line 1430 and heat sink 1495, between solder mask 1436 and heatsink 1495, between adhesive 1456 and heat sink 1495, and betweenencapsulant 1460 and heat sink 1495 while insulative base 1466 is a gel.As a result, insulative base 1466 provides a loose mechanical bondbetween routing line 1430 and heat sink 1495, between solder mask 1436and heat sink 1495, between adhesive 1456 and heat sink 1495, andbetween encapsulant 1460 and heat sink 1495. Chip 1410 and heat sink1495 are positioned relative to one another so that chip 1410 isdisposed within the periphery of heat sink 1495. Chip 1410 and heat sink1495 can be aligned using an automated pattern recognition system.

Thereafter, the structure is placed in an oven and insulative base 1466is fully cured (C stage) at relatively low temperature in the range of200 to 250° C. to form a solid adhesive insulative thermosettingpolyimide layer that mechanically attaches heat sink 1495 to thestructure.

Thereafter, metal pillar 1440 and encapsulant 1460 are grinded and thenplated contact terminal 1470 is formed (without the nickel and goldlayers).

Thereafter, the structure is dipped in an activator solution such asdilute palladium chloride of approximately 0.1 grams of palladiumchloride and 5 cubic centimeters of hydrochloric acid per liter of waterto render plated contact terminal 1470 and heat sink 1495 catalytic toelectroless nickel, and then the structure is rinsed in distilled waterto remove the palladium from encapsulant 1460 and insulative base 1466.

Thereafter, plated terminal 1480 is formed. Plated terminal 1480contacts and coats heat sink 1495 and covers heat sink 1495 in thedownward direction. As a result, plated terminal 1480 reduces corrosion.

Heat sink 1495 is spaced and separated from, electrically isolated from,overlapped by and disposed downwardly beyond chip 1410, routing line1430, solder mask 1436, metal pillar 1440, adhesive 1456, connectionjoint 1458, encapsulant 1460 and plated contact terminal 1470. Theopening (corresponding to opening 178) in insulative base 1466 and thesolder terminal (corresponding to solder terminal 182) are omitted.

Semiconductor chip assembly 1498 includes chip 1410, routing line 1430,solder mask 1436, metal pillar 1440, adhesive 1456, connection joint1458, encapsulant 1460, insulative base 1466, plated contact terminal1470, plated terminal 1480 and heat sink 1495.

FIGS. 33A, 33B and 33C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with afifteenth embodiment of the present invention. In the fifteenthembodiment, the assembly includes a ground plane. For purposes ofbrevity, any description in the first embodiment is incorporated hereininsofar as the same is applicable, and the same description need not berepeated. Likewise, elements of the fifteenth embodiment similar tothose in the first embodiment have corresponding reference numeralsindexed at fifteen-hundred rather than one-hundred. For instance, chip1510 corresponds to chip 110, routing line 1530 corresponds to routingline 130, etc.

Routing line 1530 is formed in the same manner as routing line 1030, andtherefore includes an additional enlarged circular portion (not shown)with a diameter of 400 microns at the side opposite the enlargedcircular portion (corresponding to enlarged circular portion 134).

Insulative base 1566 and ground plane 1596 are formed and attached tothe structure in the same manner as insulative base 1466 and heat sink1495, respectively, except that ground plane 1596 includes opening 1597with a diameter of 200 microns that is vertically aligned with theadditional enlarged circular portion of routing line 1530.

Opening 1578 is formed through insulative base 1566 in essentially thesame manner as opening 1078. Namely, the laser drills through andremoves portions of insulative base 1566 within the surface area ofopening 1597, thereby effecting a pattern transfer of opening 1597through insulative base 1566 to routing line 1530. A brief cleaning stepcan then be applied to remove oxides and debris that may be present onthe exposed portion of routing line 1530.

Thereafter, metal pillar 1540 and encapsulant 1560 are grinded and thenplated contact terminal 1570 is formed (without the nickel and goldlayers).

Thereafter, the structure is dipped in an activator solution such asdilute palladium chloride of approximately 0.1 grams of palladiumchloride and 5 cubic centimeters of hydrochloric acid per liter of waterto render plated contact terminal 1570 and ground plane 1596 catalyticto electroless nickel, and then the structure is rinsed in distilledwater to remove the palladium from encapsulant 1560 and insulative base1566.

Thereafter, plated terminals 1580A and 1580B are formed in the samemanner as plated terminal 1480. Plated terminal 1580A contacts routingline 1530 in opening 1578 and is spaced from ground plane 1596, andplated terminal 1580B contacts and coats ground plane 1596 and extendsinto and forms a plated through-hole (PTH) in opening 1597. Furthermore,plated terminals 1580A and 1580B are spaced and separated from oneanother.

Thereafter, solder paste is deposited on plated terminals 1580A and1580B in openings 1578 and 1597, respectively, and then the solder pasteis heated and reflowed. The solder paste cools and solidifies intosolder terminal 1582. Solder terminal 1582 contacts and electricallyconnects plated terminals 1580A and 1580B, thereby electricallyconnecting routing line 1530 and ground plane 1596.

Ground plane 1596 is electrically connected to routing line 1530, metalpillar 1540, connection joint 1558, plated contact terminal 1570 andplated terminals 1580A and 1580B, and is spaced and separated from,overlapped by and disposed downwardly beyond chip 1510, routing line1530, solder mask 1536, metal pillar 1540, adhesive 1556, connectionjoint 1558, encapsulant 1560, plated contact terminal 1570, platedterminal 1580A and solder terminal 1582. Furthermore, solder terminal1582 does not protrude downwardly beyond ground plane 1596, and servesas an interconnect rather than a contact terminal.

Semiconductor chip assembly 1598 includes chip 1510, routing line 1530,solder mask 1536, metal pillar 1540, adhesive 1556, connection joint1558, encapsulant 1560, insulative base 1566, plated contact terminal1570, plated terminals 1580A and 1580B, solder terminal 1582 and groundplane 1596.

FIGS. 34A, 34B and 34C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly in accordance with asixteenth embodiment of the present invention. In the sixteenthembodiment, the assembly is a multi-chip package. For purposes ofbrevity, any description in the first embodiment is incorporated hereininsofar as the same is applicable, and the same description need not berepeated. Likewise, elements of the sixteenth embodiment similar tothose in the first embodiment have corresponding reference numeralsindexed at sixteen-hundred rather than one-hundred. For instance, chip1610 corresponds to chip 110, routing line 1630 corresponds to routingline 130, etc.

Chip 1610 is mechanically attached to routing line 1630, solder mask1636 and metal pillar 1640 by adhesive 1656 and electrically connectedto routing line 1630 by connection joint 1658. Furthermore, metal pillar1640 is formed with a height of 700 microns (rather than 475 microns).This is accomplished by a slight adjustment to the welding operationpreviously described for metal pillar 140. In particular, the wire(corresponding to wire 146) is fractured 665 microns (rather than 440microns) over ball bond 1650, and stem 1652 has a height of 665 microns(rather than 440 microns).

Thereafter, adhesive 1657 is deposited as a spacer paste that includessilicon spacers on chip 1610, then chip 1611 (which includes pad 1617and is essentially identical to chip 1610) is placed on adhesive 1657such that adhesive 1657 contacts and is sandwiched between chips 1610and 1611, and then the structure is placed in an oven and adhesive 1657is fully cured (C stage) at relatively low temperature in the range of200 to 250° C. to form a solid adhesive insulative layer thatmechanically attaches chips 1610 and 1611. Adhesive 1657 is 100 micronsthick between chips 1610 and 1611, and chips 1610 and 1611 are spacedand separated from and vertically aligned with one another. A suitablespacer paste is Hysol QMI 500.

Thereafter, chip 1611 is wire bonded to routing line 1630 by connectionjoint 1659 in the same manner that chip 1610 is wire bonded to routingline 1630 by connection joint 1658.

Thereafter, encapsulant 1660 with a thickness of 900 microns (ratherthan 600 microns) is formed so that encapsulant 1660 contacts and coverschips 1610 and 1611, solder mask 1636, metal pillar 1640, adhesives 1656and 1657 and connection joints 1658 and 1659, then the metal base(corresponding to metal base 120) is removed, then insulative base 1666is formed, then metal pillar 1640 and encapsulant 1660 are grinded andthen plated contact terminal 1670, plated terminal 1680 and solderterminal 1682 are formed.

The semiconductor chip assembly is a multi-chip first-level package.Chips 1610 and 1611 are embedded in encapsulant 1660. Metal pillar 1640extends across most of the thickness of chip 1610 and all of thethickness of chip 1611. Furthermore, an electrically conductive pathbetween pad 1616 and metal pillar 1640 not only includes but alsorequires routing line 1630, and an electrically conductive path betweenpad 1617 and metal pillar 1640 not only includes but also requiresrouting line 1630. Thus, chips 1610 and 1611 are both embedded inencapsulant 1660 and electrically connected to metal pillar 1640 by anelectrically conductive path that includes routing line 1630.

Semiconductor chip assembly 1698 includes chips 1610 and 1611, routingline 1630, solder mask 1636, metal pillar 1640, adhesives 1656 and 1657,connection joints 1658 and 1659, encapsulant 1660, insulative base 1666,plated contact terminal 1670, plated terminal 1680 and solder terminal1682.

The semiconductor chip assemblies described above are merely exemplary.Numerous other embodiments are contemplated. For instance, the soldermask, adhesive, insulative base, metal base, plated terminal and/orsolder terminal can be omitted. In addition, the embodiments describedabove can generally be combined with one another. For instance, theflip-chip in the second embodiment and the connection joints in thethird and fourth embodiments can be used in the other embodiments exceptfor the multi-chip assembly in the sixteenth embodiment since the chipsare not inverted. Likewise, the metal pillar in the fifth embodiment,the plated contact terminal in the sixth embodiment and the encapsulantin the seventh embodiment can be used in the other embodiments.Likewise, the encapsulant in the eighth embodiment can be used in theother embodiments except for the multi-chip assembly in the sixteenthembodiment since the chips are not inverted. Likewise, the solder maskin the ninth embodiment can be used in the other embodiments. Likewise,the solder terminal in the tenth embodiment can be used in the otherembodiments except for the eleventh, fourteenth and fifteenthembodiments since the conductive trace is not exposed in the downwarddirection. Likewise, the omission of the solder terminal in the eleventhembodiment can be used in the other embodiments. Likewise, the taperedpillar in the twelfth embodiment can be used in the other embodimentsexcept for the eleventh, fourteenth and fifteenth embodiments since theconductive trace is not exposed in the downward direction. Likewise, thesubstrate in the thirteenth embodiment can be used in the otherembodiments. Likewise, the heat sink and the ground plane in thefourteenth and fifteenth embodiments can be used the other embodimentsexcept for the tenth and twelfth embodiments since the conductive traceis exposed in the downward direction. Finally, the multi-chip assemblyin the sixteenth embodiment can be used in the other embodiments exceptfor the second to fourth and eighth embodiments since the chips areinverted. The embodiments described above can be mixed-and-matched withone another and with other embodiments depending on design andreliability considerations.

The metal base can be various metals such as copper, copper alloys,nickel, iron-nickel alloys, aluminum, and so on, and can be a singlelayer or multiple layers.

The metal base need not necessarily be removed. For instance, a portionof the metal base that extends across the pad can be selectively etchedto permit formation of the through-hole, and another portion of themetal base that is disposed within the periphery of the chip can remainintact and provide a heat sink. Likewise, a portion of the metal basewithin the periphery of the chip can be selectively etched, and anotherportion of the metal base that is disposed outside the periphery of thechip can remain intact and provide the tapered pillar.

The etch mask that defines the tapered pillar can be a wide variety ofmaterials including copper, gold, nickel, palladium, tin, solder,photoresist and epoxy, can be formed by a wide variety of processesincluding electroplating, electroless plating, printing, reflowing andcuring, and can have a wide variety of shapes and sizes. The etch maskcan be deposited on the metal base before, during or after the routingline is deposited on the metal base and before or after the encapsulantis formed, can be disposed on a planar surface of the metal base or in arecess in the metal base, and if disposed in a recess need notnecessarily fill the recess. Furthermore, the etch mask can remainpermanently attached to the tapered pillar or be removed after thetapered pillar is formed.

The etch mask that defines the tapered pillar is undercut by a wetchemical etch that forms the tapered pillar but can subsequently beconfined to the tip of the tapered pillar, for instance by dislodging aportion of the etch mask outside the tip of the tapered pillar bymechanical brushing, sand blasting, air blowing or water rinsing, or byreflowing a solder etch mask when the tapered pillar does not provide awettable surface. Alternatively, a solder etch mask can be reflowed toconformally coat the tapered pillar, for instance by depositing flux onthe tapered pillar so that the tapered pillar provides a wettablesurface before the solder reflow operation.

Further details regarding a tapered pillar that is etched from a metalbase and contacts a routing line are disclosed in U.S. application Ser.No. 10/714,794 filed Nov. 17, 2003 by Chuen Rong Leu et al. entitled“Semiconductor Chip Assembly with Embedded Metal Pillar” which isincorporated by reference.

The routing line can be various conductive metals including copper,gold, nickel, silver, palladium, tin, combinations thereof, and alloysthereof. The preferred composition of the routing line will depend onthe nature of the connection joint as well as design and reliabilityfactors. Furthermore, those skilled in the art will understand that inthe context of a semiconductor chip assembly, a copper material istypically a copper alloy that is mostly copper but not pure elementalcopper, such copper-zirconium (99.9% copper),copper-silver-phosphorus-magnesium (99.7% copper), orcopper-tin-iron-phosphorus (99.7% copper). Likewise, the routing linecan fan-in as well as fan-out.

The routing line can be formed on the metal base by numerous depositiontechniques including electroplating and electroless plating. Inaddition, the routing line can be deposited on the metal base as asingle layer or multiple layers. For instance, the routing line can be a10 micron layer of gold, or alternatively, a 9.5 micron layer of nickelelectroplated on a 0.5 micron layer of gold electroplated on a copperbase to reduce costs, or alternatively, a 9 micron layer of nickelelectroplated on a 0.5 micron layer of gold electroplated on a 0.5micron layer of tin electroplated on a copper base to reduce costs andavoid gold-copper alloys that may be difficult to remove when the copperbase is etched. As another example, the routing line can consist of anon-copper layer electroplated on a copper base and a copper layerelectroplated on the non-copper layer. Suitable non-copper layersinclude nickel, gold, palladium and silver. After the routing line isformed, a wet chemical etch can be applied that is highly selective ofcopper with respect to the non-copper layer to etch the copper base andexpose the routing line without removing the copper or non-copperlayers. The non-copper layer provides an etch stop that prevents the wetchemical etch from removing the copper layer. Furthermore, it isunderstood that in the context of the present invention, the routingline and the metal base are different metals (or metallic materials)even if a multi-layer routing line includes a single layer that issimilar to the metal base (such as the example described above) or asingle layer of a multi-layer metal base.

The routing line can also be formed by etching a metal layer attached tothe metal base. For instance, a photoresist layer can be formed on themetal layer, the metal layer can be etched using the photoresist layeras an etch mask, and then the photoresist layer can be stripped.Alternatively, a photoresist layer can be formed on the metal layer, aplated metal can be selectively electroplated on the metal layer usingthe photoresist layer as a plating mask, the photoresist layer can bestripped, and then the metal layer can be etched using the plated metalas an etch mask. In this manner, the routing line can be formedsemi-additively and include unetched portions of the metal layer and theplated metal. Likewise, the routing line can be formed subtractivelyfrom the metal layer, regardless of whether the plated metal etch maskremains attached to the routing line.

The routing line can be spot plated near the pad to make it compatiblewith receiving the connection joint. For instance, a copper routing linecan be spot plated with nickel and then silver to make it compatiblewith a gold ball bond connection joint and avoid the formation ofbrittle silver-copper intermetallic compounds. The routing line can alsobe spot plated away from the pad to make it compatible with receivingthe metal pillar. For instance, a copper routing line can be spot platedwith nickel and then gold to facilitate welding a gold metal pillar.

The metal pillar can be welded to the routing line by thermocompressionbonding, thermosonic bonding, ultrasonic bonding, and other approachesusing a combination of heat, pressure and/or vibration without usingmaterial other than the materials of the metal pillar and the routingline to provide the weld. It is understood that incidental amounts ofother materials such as surface preparation agents, reaction productsand contaminants such as oxide coatings and the like may be present inor around the weld.

The metal pillar may be composed of various metals including gold,silver, copper, nickel, aluminum, palladium, indium and alloys thereofas well as solder coated over these metals. For instance, gold alloyedwith a small amount of beryllium exhibits grain growth at lowtemperature which enhances stability and increases strength byprecipitation hardening. Gold alloyed with 5 to 10 ppm beryllium byweight or 30 to 100 ppm copper by weight is commonly used forthermocompression and thermosonic wire bonding. Furthermore, aluminumalloyed with small amounts of silicon, magnesium or both has beenproposed for thermosonic wire bonding.

The metal pillar may be formed by contacting a wire ball to the routingline using a capillary. Furthermore, the capillary can be withdrawn(clamp open) and then reapplied (clamp closed) to supply additional wireto the wire ball.

The metal pillar can be uncovered in the upward direction by theencapsulant or any other insulative material of the assembly. Forinstance, the metal pillar can be unexposed in the upward direction andthe plated contact terminal can be exposed in the upward direction, oralternatively, the metal pillar can be unexposed in the upwarddirection, the plated contact terminal can be unexposed in the upwarddirection, and the metal pillar and the plated contact terminal can becovered in the upward direction by an insulative material external tothe assembly such as another semiconductor chip assembly in a stackedarrangement.

The plated contact terminal can be various conductive metals includingcopper, gold, nickel, silver, palladium, tin, combinations thereof, andalloys thereof, can be formed by electroplating, electroless plating orcombinations thereof, and can have a wide variety of shapes and sizes.In addition, the plated contact terminal can be deposited on the metalpillar as a single layer or multiple layers. For instance, the platedcontact terminal can be an electrolessly plated nickel layer, oralternatively, an electrolessly plated gold layer on an electrolesslyplated nickel layer on an electroplated copper layer. Furthermore, theplated contact terminal can include electrolessly plated layers that areformed simultaneously with or independently of the plated terminal.

The conductive trace can function as a signal, power or ground layerdepending on the purpose of the associated chip pad.

The pad can have numerous shapes including a flat rectangular shape anda bumped shape. If desired, the pad can be treated to accommodate theconnection joint.

Numerous adhesives can be applied to mechanically attach the chip to therouting line. For instance, the adhesive can be applied as a paste, alaminated layer, or a liquid applied by screen-printing, spin-on, orspray-on. The adhesive can be a single layer that is applied to themetal base or the solder mask and then contacted to the chip or a singlelayer that is applied to the chip and then contacted to the metal baseor the solder mask. Similarly, the adhesive can be multiple layers witha first layer applied to the metal base or the solder mask, a secondlayer applied to the chip and then the layers contacted to one another.Thermosetting adhesive liquids and pastes such as epoxies are generallysuitable. Likewise, thermoplastic adhesives such as an insulativethermoplastic polyimide film with a glass transition temperature (Tg) of400° C. are also generally suitable. Silicone adhesives are alsogenerally suitable.

The insulative base may be rigid or flexible, and can be variousdielectric films or prepregs formed from numerous organic or inorganicinsulators such as tape (polyimide), epoxy, silicone, glass, aramid andceramic. Organic insulators are preferred for low cost, high dielectricapplications, whereas inorganic insulators are preferred when highthermal dissipation and a matched thermal coefficient of expansion areimportant. For instance, the insulative base can initially be an epoxypaste that includes an epoxy resin, a curing agent, an accelerator and afiller, that is subsequently cured or hardened to form a solid adherentinsulative layer. The filler can be an inert material such as silica(powdered fused quartz) that improves thermal conductivity, thermalshock resistance and thermal coefficient of expansion matching. Organicfiber reinforcement may also be used in resins such as epoxy, cyanateester, polyimide, PTFE and combinations thereof. Fibers that may be usedinclude aramid, polyester, polyamide, poly-ether-ether-ketone,polyimide, polyetherimide and polysulfone. The fiber reinforcement canbe woven fabric, woven glass, random microfiber glass, woven quartz,woven, aramid, non-woven fabric, non-woven aramid fiber or paper.Commercially available dielectric materials such as SPEEDBOARD C prepregby W.L. Gore & Associates of Eau Claire, Wis. are suitable.

The insulative base can be deposited in numerous manners, includingprinting and transfer molding. Furthermore, the insulative base can beformed before or after attaching the chip and the metal pillar to therouting line, before or after forming the encapsulant and before orafter removing the upper portion of the encapsulant. For instance, themetal base can be removed and the insulative base can be formed afterforming the encapsulant and before removing the upper portion of theencapsulant, or alternatively, after removing the upper portion of theencapsulant.

The encapsulant can be deposited using a wide variety of techniquesincluding printing and transfer molding. For instance, the encapsulantcan be printed on the chip and the metal pillar as an epoxy paste andthen cured or hardened to form a solid adherent protective layer. Theencapsulant can be any of the adhesives mentioned above. Moreover, theencapsulant need not necessarily contact the chip or the metal pillar.For instance, a glob-top coating can be deposited on the chip afterattaching the chip to the routing line, and then the encapsulant can beformed on the glob-top coating. Likewise, a coating (such as flux orsolder) can be deposited on the metal pillar, and then the encapsulantcan be formed on the coating.

The encapsulant can have its upper portion removed using a wide varietyof techniques including grinding (including mechanical polishing andchemical-mechanical polishing), blanket laser ablation and blanketplasma etching. Likewise, the encapsulant can have a selected portionabove the metal pillar removed using a wide variety of techniquesincluding selective laser ablation, selective plasma etching andphotolithography.

The encapsulant can be laterally aligned with the metal pillar along anupwardly facing surface that faces and extends vertically beyond thechip by grinding the encapsulant without grinding the chip or the metalpillar, and then grinding the encapsulant and the metal pillar withoutgrinding the chip, and then discontinuing the grinding before reachingthe chip.

The encapsulant can be laterally aligned with the chip and the metalpillar along an upwardly facing surface by grinding the encapsulantwithout grinding the chip or the metal pillar, then grinding theencapsulant and the metal pillar without grinding the chip, and thengrinding the encapsulant, the chip and the metal pillar (if the metalpillar extends upwardly beyond the chip before the grinding occurs), oralternatively, by grinding the encapsulant without grinding the chip orthe metal pillar, then grinding the encapsulant and the chip withoutgrinding the metal pillar, and then grinding the encapsulant, the chipand the metal pillar (if the chip extends upwardly beyond the metalpillar before the grinding occurs).

The connection joint can be formed from a wide variety of materialsincluding copper, gold, nickel, palladium, tin, alloys thereof, andcombinations thereof, can be formed by a wide variety of processesincluding electroplating, electroless plating, ball bonding, wirebonding, stud bumping, solder reflowing, conductive adhesive curing, andwelding, and can have a wide variety of shapes and sizes. The shape andcomposition of the connection joint depends on the composition of therouting line as well as design and reliability considerations. Furtherdetails regarding an electroplated connection joint are disclosed inU.S. application Ser. No. 09/865,367 filed May 24, 2001 by Charles W. C.Lin entitled “Semiconductor Chip Assembly with SimultaneouslyElectroplated Contact Terminal and Connection Joint” which isincorporated by reference. Further details regarding an electrolesslyplated connection joint are disclosed in U.S. application Ser. No.09/864,555 filed May 24, 2001 by Charles W. C. Lin entitled“Semiconductor Chip Assembly with Simultaneously Electrolessly PlatedContact Terminal and Connection Joint” which is incorporated byreference. Further details regarding a ball bond connection joint aredisclosed in U.S. application Ser. No. 09/864,773 filed May 24, 2001 byCharles W. C. Lin entitled “Semiconductor Chip Assembly with Ball BondConnection Joint” which is incorporated by reference. Further detailsregarding a solder or conductive adhesive connection joint are disclosedin U.S. application Ser. No. 09/927,216 filed Aug. 10, 2001 by CharlesW. C. Lin entitled “Semiconductor Chip Assembly with Hardened ConnectionJoint” which is incorporated by reference. Further details regarding awelded connection joint are disclosed in U.S. application Ser. No.10/302,642 filed Nov. 23, 2002 by Cheng-Lien Chiang et al. entitled“Method of Connecting a Conductive Trace to a Semiconductor Chip UsingPlasma Undercut Etching” which is incorporated by reference.

After the connection joint is formed, if a plating bus exists then it isdisconnected from the conductive trace. The plating bus can bedisconnected by mechanical sawing, laser cutting, chemical etching, andcombinations thereof. If the plating bus is disposed about the peripheryof the assembly but is not integral to the assembly, then the platingbus can be disconnected when the assembly is singulated from otherassemblies. However, if the plating bus is integral to the assembly, orsingulation has already occurred, then a photolithography step can beadded to selectively cut related circuitry on the assembly that isdedicated to the plating bus since this circuitry would otherwise shortthe conductive traces together. Furthermore, the plating bus can bedisconnected by etching the metal base.

A soldering material or solder ball can be deposited on the conductivetrace by plating or printing or placement techniques if required for thenext level assembly. However, the next level assembly may not requirethat the semiconductor chip assembly contain solder. For instance, inland grid array (LGA) packages, the soldering material is normallyprovided by the panel rather than the contact terminals on thesemiconductor chip assembly.

Various cleaning steps, such as a brief oxygen plasma cleaning step, ora brief wet chemical cleaning step using a solution containing potassiumpermanganate, can be applied to the structure at various stages, such asimmediately before forming the connection joint to clean the routingline and the pad.

It is understood that, in the context of the present invention, any chipembedded in the encapsulant is electrically connected to the metalpillar by an electrically conductive path that includes the routing linemeans that the routing line is in an electrically conductive pathbetween the metal pillar and any chip embedded in the encapsulant. Thisis true regardless of whether a single chip is embedded in theencapsulant (in which case the chip is electrically connected to themetal pillar by an electrically conductive path that includes therouting line) or multiple chips are embedded in the encapsulant (inwhich case each of the chips is electrically connected to the metalpillar by an electrically conductive path that includes the routingline). This is also true regardless of whether the electricallyconductive path includes or requires a connection joint between therouting line and the chip. This is also true regardless of whether theelectrically conductive path includes or requires a passive componentsuch as a capacitor or a resistor. This is also true regardless ofwhether multiple chips are electrically connected to the routing line bymultiple connection joints, and the multiple connection joints areelectrically connected to one another only by the routing line. This isalso true regardless of whether multiple chips are electricallyconnected to the metal pillar by different electrically conductive paths(such as the multiple connection joint example described above) as longas each of the electrically conductive paths includes the routing line.

It is also understood that, in the context of the present invention, themetal pillar extends across most or all of a thickness of the chip andany other chip embedded in the encapsulant means that the metal pillarextends across most or all of a thickness of any chip embedded in theencapsulant. This is true regardless of whether a single chip isembedded in the encapsulant (in which case the metal pillar extendsacross most or all of a thickness of the chip) or multiple chips areembedded in the encapsulant (in which case the metal pillar extendsacross most or all of a thickness of each of the chips).

The “upward” and “downward” vertical directions do not depend on theorientation of the assembly, as will be readily apparent to thoseskilled in the art. For instance, the metal pillar extends verticallybeyond the routing line in the “upward” direction, the encapsulantextends vertically beyond the routing line in the “upward” direction,the tapered pillar extends vertically beyond the routing line in the“downward” direction, and the insulative base extends vertically beyondthe chip in the “downward” direction, regardless of whether the assemblyis inverted and/or mounted on a printed circuit board. Likewise, therouting line extends “laterally” beyond the metal pillar towards thechip regardless of whether the assembly is inverted, rotated or slanted.Thus, the “upward” and “downward” directions are opposite one anotherand orthogonal to the “lateral” direction, and the “laterally aligned”surfaces are coplanar with one another in a lateral plane orthogonal tothe upward and downward directions. Moreover, the metal pillar is shownabove the routing line, the chip is shown above the insulative base, andthe encapsulant is shown above the routing line and the insulative basewith a single orientation throughout the drawings for ease of comparisonbetween the figures, although the assembly and its components may beinverted at various manufacturing stages.

The working format for the semiconductor chip assembly can be a singleassembly or multiple assemblies based on the manufacturing design. Forinstance, a single assembly that includes a single chip can bemanufactured individually. Alternatively, numerous assemblies can besimultaneously batch manufactured on a single metal base with a singleinsulative base and a single encapsulant and then separated from oneanother. For example, routing lines for multiple assemblies can besimultaneously electroplated on the metal base, then separate spacedsolder masks for the respective assemblies can be simultaneouslyphotolithographically patterned on the metal base and the routing lines,then the metal pillars can be welded to the corresponding routing lines,then separate spaced adhesives for the respective assemblies can beselectively disposed on the metal base, then the chips can be disposedon the corresponding adhesives, then the adhesives can be simultaneouslyfully cured, then the connection joints can be formed on thecorresponding routing lines and pads, then the encapsulant can bedeposited, then the metal base can be etched and removed, then theinsulative base can be formed, then the encapsulant and the metalpillars can be grinded, then the plated contact terminals can besimultaneously electrolessly plated on the corresponding metal pillars,then the plated terminals can be simultaneously electrolessly plated onthe corresponding routing lines, then the solder terminals can bedeposited and simultaneously reflowed on the corresponding platedterminals, and then the encapsulant and the insulative base can be cut,thereby separating the individual single chip-substrate assemblies.

The semiconductor chip assembly can have a wide variety of packagingformats as required by the next level assembly. For instance, theconductive traces can be configured so that the assembly is a grid arraysuch as a ball grid array (BGA), column grid array (CGA), land gridarray (LGA) or pin grid array (PGA).

The semiconductor chip assembly can be a first-level package that is asingle-chip package (such as the first to fifteenth embodiments) or amulti-chip package (such as the sixteenth embodiment). Furthermore, amulti-chip first-level package can include chips that are stacked andvertically aligned with one another or are coplanar and laterallyaligned with one another.

Advantageously, the semiconductor chip assembly of the present inventionis reliable and inexpensive. The encapsulant and the insulative base canprotect the chip from handling damage, provide a known dielectricbarrier for the conductive trace and protect the assembly fromcontaminants and unwanted solder reflow during the next level assembly.The encapsulant can provide mechanical support for the conductive traceafter the metal base is removed. The mode of the chip connection canshift from the initial mechanical coupling to metallurgical coupling toassure sufficient metallurgical bond strength. The conductive trace caninclude a robust, permanent weld between the routing line and the metalpillar that enhances strength and reliability. Furthermore, theconductive trace can be mechanically and metallurgically coupled to thechip without wire bonding, TAB, solder or conductive adhesive, althoughthe process is flexible enough to accommodate these techniques ifdesired. The process is highly versatile and permits a wide variety ofmature connection joint technologies to be used in a unique and improvedmanner. The metal pillar can extend vertically across most or all of thechip thickness and the conductive trace can extend vertically across theassembly thickness and be exposed in the upward and downward directionsto provide vertical routing that facilitates a three-dimensional stackedarrangement. Furthermore, the tapered pillar is particularly well-suitedfor reducing thermal mismatch related stress in the next level assemblyand yields enhanced reliability for the next level assembly that exceedsthat of conventional BGA packages. As a result, the assembly of thepresent invention significantly enhances throughput, yield andperformance characteristics compared to conventional packagingtechniques. Moreover, the assembly of the present invention iswell-suited for use with materials compatible with copper chiprequirements.

Various changes and modifications to the presently preferred embodimentsdescribed herein will be apparent to those skilled in the art. Forinstance, the materials, dimensions and shapes described above aremerely exemplary. Such changes and modifications may be made withoutdeparting from the spirit and scope of the present invention as definedin the appended claims.

1. A semiconductor chip assembly, comprising: a semiconductor chip thatincludes first and second opposing surfaces, wherein the first surfaceof the chip includes a conductive pad; a conductive trace that includesa routing line, a metal pillar and a plated contact terminal, whereinthe metal pillar is metallurgically welded to and only to the routingline and consists of a ball bond and an elongated stem; the ball bond iswelded to the routing line; the stem extends from the ball bond, isspaced from the routing line and includes a distal end that faces awayfrom the ball bond; and the plated contact terminal is plated on andonly on the distal end; a connection joint that electrically connectsthe routing line and the pad; and an encapsulant that includes first andsecond opposing surfaces, wherein the first surface of encapsulant facesin a first direction; the second surface of the encapsulant faces in asecond direction opposite the first direction; the chip and the metalpillar are embedded in the encapsulant; the chip, the metal pillar andthe encapsulant extend vertically beyond the routing line in the firstdirection; the routing line extends laterally beyond the metal pillartowards the chip and extends vertically beyond the chip and the metalpillar in the second direction; the metal pillar is disposed outside aperiphery of the chip and extends vertically across most or all of athickness of the chip between the first and second surfaces of the chip;the stem extends vertically beyond the ball bond in the first directionand extends vertically farther than the ball bond; the distal end islaterally aligned with the first surface of the encapsulant and disposedwithin a periphery of the plated contact terminal; and the platedcontact terminal extends vertically beyond the chip, the metal pillarand the encapsulant in the first direction, has a dome-like shape withan apex that faces in the first direction and has a diameter that is atleast twice as large as a diameter of the distal end.
 2. The assembly ofclaim 1, wherein the chip is the only chip embedded in the encapsulant.3. The assembly of claim 1, wherein the routing line is disposedvertically beyond the chip and the metal pillar in the second direction.4. The assembly of claim 1, wherein the metal pillar extends verticallybeyond the chip in the first direction.
 5. The assembly of claim 1,wherein the metal pillar extends vertically beyond the chip in thesecond direction.
 6. The assembly of claim 1, wherein the metal pillarextends vertically beyond the chip in the first and second directions.7. The assembly of claim 1, wherein the metal pillar is disposed withina periphery of the routing line.
 8. The assembly of claim 1, wherein themetal pillar is disposed within a periphery of the plated contactterminal.
 9. The assembly of claim 1, wherein the metal pillar isdisposed within a periphery of the routing line and a periphery of theplated contact terminal.
 10. The assembly of claim 1, wherein the metalpillar is not covered in the first direction by the encapsulant or anyother insulative material of the assembly.
 11. The assembly of claim 1,wherein the metal pillar is not covered in the second direction by theencapsulant or any other insulative material of the assembly.
 12. Theassembly of claim 1, wherein the metal pillar does not contact anyelectrical conductor other than the routing line and the plated contactterminal.
 13. The assembly of claim 1, wherein the metal pillar does notcontact any material other than the routing line, the plated contactterminal and the encapsulant.
 14. The assembly of claim 1, wherein theball bond has a diameter that is at least twice as large a diameter ofthe stem.
 15. The assembly of claim 1, wherein the ball bond has adiameter that is at least twice as large as a diameter of the distalend.
 16. The assembly of claim 1, wherein the ball bond has a diameterthat is at least twice as large as a diameter of the distal end, and theplated contact terminal has a diameter that is at least twice as largeas a diameter of the ball bond.
 17. The assembly of claim 1, wherein thestem is disposed within a periphery of the ball bond, and the ball bondis disposed within a periphery of the plated contact terminal.
 18. Theassembly of claim 17, wherein the ball bond has a diameter that is atleast twice as large as a diameter of the distal end, and the platedcontact terminal has a diameter that is at least twice as large as adiameter of the ball bond.
 19. The assembly of claim 1, wherein the stemis straight.
 20. The assembly of claim 1, wherein the stem has a uniformdiameter.
 21. The assembly of claim 1, wherein the stem extends acrossmost or all of the thickness of the chip.
 22. The assembly of claim 1,wherein the plated contact terminal is electroplated metal.
 23. Theassembly of claim 1, wherein the plated contact terminal iselectrolessly plated metal.
 24. The assembly of claim 1, wherein theplated contact terminal has a diameter that is at least twice as largeas a diameter of the ball bond.
 25. The assembly of claim 1, wherein theplated contact terminal has a diameter that is at least four times aslarge as a diameter of the distal end.
 26. The assembly of claim 1,wherein the plated contact terminal has a hemispherical shape thatincludes a convex surface and a flat surface, the convex surfaceincludes the apex and is spaced from the metal pillar and theencapsulant, and the flat surface contacts the metal pillar and theencapsulant.
 27. The assembly of claim 1, wherein the connection jointis a wire bond.
 28. The assembly of claim 1, wherein the encapsulantcovers the chip.
 29. The assembly of claim 1, wherein the encapsulantcontacts the chip, the ball bond, the stem and the plated contactterminal.
 30. The assembly of claim 1, wherein the first surface of theencapsulant is laterally aligned with the second surface of the chip.31. The assembly of claim 1, including an insulative base that contactsthe routing line, is spaced from and overlapped by the chip and extendsvertically beyond the chip, the metal pillar and the encapsulant in thesecond direction.
 32. The assembly of claim 1, including an insulativeadhesive that contacts the chip and extends vertically beyond the chipin the second direction.
 33. The assembly of claim 1, including a solderterminal that is electrically connected to the routing line, extendsvertically beyond the routing line and the encapsulant in the seconddirection and is spaced from the metal pillar and the connection joint.34. The assembly of claim 1, including a tapered pillar that contactsand is not metallurgically welded to the routing line, is disposedoutside the periphery of the chip, is overlapped by the metal pillar andextends vertically beyond the chip, the routing line, the metal pillarand the encapsulant in the second direction.
 35. The assembly of claim34, wherein the metal pillar and the tapered pillar are verticallyaligned with one another.
 36. The assembly of claim 34, wherein thetapered pillar includes first and second opposing surfaces that are flatand parallel to one another and tapered sidewalls therebetween, thefirst surface of the tapered pillar faces towards and contacts therouting line, the second surface of the tapered pillar faces away fromand is spaced from the routing line, and the tapered sidewalls slantinwardly towards the second surface of the tapered pillar.
 37. Theassembly of claim 36, wherein the second surface of the tapered pillaris concentrically disposed within a surface area of the first surface ofthe tapered pillar, and a surface area of the first surface of thetapered pillar is at least 20 percent larger than a surface area of thesecond surface of the tapered pillar.
 38. The assembly of claim 1,wherein the assembly is a first-level package.
 39. The assembly of claim38, including a heat sink that is mechanically attached to the chip,electrically isolated from the chip, overlapped by the chip and disposedvertically beyond the chip and the conductive trace in the seconddirection.
 40. The assembly of claim 38, including a ground plane thatis mechanically attached to the routing line, electrically connected tothe routing line, overlapped by the routing line and disposed verticallybeyond the chip and the routing line in the second direction.
 41. Asemiconductor chip assembly, comprising: a semiconductor chip thatincludes first and second opposing surfaces, wherein the first surfaceof the chip includes a conductive pad; a conductive trace that includesa routing line, a metal pillar and a plated contact terminal, whereinthe metal pillar is metallurgically welded to and only to the routingline and consists of a ball bond and an elongated stem; the ball bond iswelded to the routing line; the stem extends from the ball bond, isspaced from the routing line and includes a distal end that faces awayfrom the ball bond; and the plated contact terminal is plated on andonly on the distal end; a connection joint that electrically connectsthe routing line and the pad; and an encapsulant that includes first andsecond opposing surfaces, wherein the first surface of encapsulant facesin a first direction; the second surface of the encapsulant faces in asecond direction opposite the first direction; the chip and the metalpillar are embedded in the encapsulant; the chip, the metal pillar andthe encapsulant extend vertically beyond the routing line in the firstdirection; the routing line extends laterally beyond the metal pillartowards the chip and extends vertically beyond the chip and the metalpillar in the second direction; the metal pillar is disposed outside aperiphery of the chip, extends vertically across most or all of athickness of the chip between the first and second surfaces of the chipand does not contact any electrical conductor other than the routingline and the plated contact terminal; the stem extends vertically beyondthe ball bond in the first direction and extends vertically farther thanthe ball bond; the distal end is laterally aligned with the firstsurface of the encapsulant and disposed within a periphery of the platedcontact terminal; and the plated contact terminal extends verticallybeyond the chip, the metal pillar and the encapsulant in the firstdirection, has a dome-like shape with an apex that faces in the firstdirection and has a diameter that is at least as large as a diameter ofthe ball bond and at least twice as large as a diameter of the distalend.
 42. The assembly of claim 41, wherein the chip is the only chipembedded in the encapsulant.
 43. The assembly of claim 41, wherein therouting line is disposed vertically beyond the chip and the metal pillarin the second direction, and the metal pillar is disposed within aperiphery of the routing line and a periphery of the plated contactterminal.
 44. The assembly of claim 41, wherein the metal pillar extendsvertically beyond the chip in the first and second directions.
 45. Theassembly of claim 41, wherein the ball bond has a diameter that is atleast twice as large as a diameter of the distal end, and the platedcontact terminal has a diameter that is at least twice as large as adiameter of the ball bond.
 46. The assembly of claim 41, wherein thestem is straight, has a uniform diameter and extends across most or allof the thickness of the chip.
 47. The assembly of claim 41, wherein theplated contact terminal has a hemispherical shape that includes a convexsurface and a flat surface, the convex surface includes the apex and isspaced from the metal pillar and the encapsulant, and the flat surfacecontacts the metal pillar and the encapsulant.
 48. The assembly of claim41, wherein the encapsulant contacts the chip, the ball bond, the stemand the plated contact terminal.
 49. The assembly of claim 41, includinga tapered pillar that contacts and is not metallurgically welded to therouting line, is disposed outside the periphery of the chip, isoverlapped by the metal pillar and extends vertically beyond the chip,the routing line, the metal pillar and the encapsulant in the seconddirection, wherein the metal pillar and the tapered pillar arevertically aligned with and spaced from one another, the tapered pillaris not embedded in the encapsulant, the tapered pillar includes firstand second opposing surfaces that are flat and parallel to one anotherand tapered sidewalls therebetween, the first surface of the taperedpillar faces towards and contacts the routing line, the second surfaceof the tapered pillar faces away from and is spaced from the routingline, and the tapered sidewalls slant inwardly towards the secondsurface of the tapered pillar.
 50. The assembly of claim 41, wherein theassembly is a first-level package.
 51. A method of making asemiconductor chip assembly, comprising: providing a routing line; thenmechanically attaching a semiconductor chip to the routing line, whereinthe chip includes first and second opposing surfaces, and the firstsurface of the chip includes a conductive pad; forming a connectionjoint that electrically connects the routing line and the pad;metallurgically welding a metal pillar to and only to the routing line,wherein the metal pillar consists of a ball bond and an elongated stem,the ball bond is welded to the routing line and the stem extends fromthe ball bond and is spaced from the routing line; forming anencapsulant after attaching the chip to the routing line and welding themetal pillar to the routing line, wherein the encapsulant includes afirst surface that faces in a first direction and a second surface thatfaces in a second direction opposite the first direction, the chip andthe metal pillar are embedded in the encapsulant, the encapsulant coversand extends vertically beyond the chip, the routing line and the metalpillar in the first direction, the chip and the metal pillar extendvertically beyond the routing line in the first direction, the routingline extends laterally beyond the metal pillar towards the chip andextends vertically beyond the chip and the metal pillar in the seconddirection, the metal pillar is disposed outside a periphery of the chipand extends vertically across most or all of a thickness of the chipbetween the first and second surfaces of the chip, and the stem extendsvertically beyond the ball bond in the first direction and extendsvertically farther than the ball bond; removing a portion of theencapsulant such that a distal end of the stem is exposed; and thenplating a plated contact terminal on and only on the distal end, whereinthe plated contact terminal extends vertically beyond the chip, themetal pillar and the encapsulant in the first direction, covers thedistal end in the first direction and has a diameter that is at leasttwice as large as a diameter of the distal end.
 52. The method of claim51, wherein providing the routing line includes selectively depositingthe routing line on a metal base, attaching the chip to the routing lineincludes positioning the chip such that the metal base extendsvertically beyond the chip in the second direction, and after formingthe encapsulant, etching the metal base thereby reducing contact areabetween the metal base and the routing line.
 53. The method of claim 52,wherein forming the routing line includes: providing a plating mask onthe metal base, wherein the plating mask includes an opening thatexposes a portion of the metal base; and then electroplating the routingline on the exposed portion of the metal base through the opening in theplating mask.
 54. The method of claim 52, wherein etching the metal baseremoves a first portion of the metal base that contacts the routing linewithout removing a second portion of the metal base that contacts therouting line, thereby reducing but not eliminating contact area betweenthe metal base and the routing line.
 55. The method of claim 52, whereinetching the metal base removes a first portion of the metal base withina periphery of the pad without removing a second portion of the metalbase outside the periphery of the pad.
 56. The method of claim 52,wherein etching the metal base forms a tapered pillar from an unetchedportion of the metal base, and the tapered pillar contacts the routingline, is disposed outside the periphery of the chip, is overlapped bythe metal pillar and extends vertically beyond the chip, the routingline, the metal pillar and the encapsulant in the second direction. 57.The method of claim 52, wherein etching the metal base eliminatescontact area between the metal base and the routing line.
 58. The methodof claim 52, wherein etching the metal base removes the metal base. 59.The method of claim 52, wherein etching the metal base electricallyisolates the routing line from other routing lines formed on the metalbase.
 60. The method of claim 52, wherein etching the metal baseelectrically isolates the pad from other conductive pads of the chip.61. The method of claim 52, wherein plating the plated contact terminalon the distal end includes electroplating the plated contact terminal onthe distal end using the metal base, the routing line and the metalpillar as a plating bus before etching the metal base.
 62. The method ofclaim 52, wherein plating the plated contact terminal on the distal endincludes electrolessly plating the plated contact terminal on the distalend after etching the metal base.
 63. The method of claim 51, whereinwelding the metal pillar to the routing line includes thermocompressionbonding.
 64. The method of claim 51, wherein welding the metal pillar tothe routing line includes thermosonic bonding.
 65. The method of claim51, wherein welding the metal pillar to the routing line includesultrasonic bonding.
 66. The method of claim 51, wherein forming theencapsulant includes transfer molding.
 67. The method of claim 51,wherein removing the portion of the encapsulant includes grinding theencapsulant.
 68. The method of claim 51, wherein removing the portion ofthe encapsulant includes grinding the encapsulant without grinding thestem, and then grinding the encapsulant and the stem.
 69. The method ofclaim 68, wherein removing the portion of the encapsulant laterallyaligns the first surface of the encapsulant and the distal end.
 70. Themethod of claim 51, wherein removing the portion of the encapsulantincludes grinding the encapsulant without grinding the stem and withoutgrinding the chip, then grinding the encapsulant and the stem withoutgrinding the chip, and then grinding the encapsulant, the stem and thechip.
 71. The method of claim 70, wherein removing the portion of theencapsulant exposes the second surface of the chip and laterally alignsthe first surface of the encapsulant, the second surface of the chip andthe distal end.
 72. The method of claim 51, wherein plating the platedcontact terminal on the distal end includes electroplating the platedcontact terminal on the distal end.
 73. The method of claim 51, whereinplating the plated contact terminal on the distal end includeselectrolessly plating the plated contact terminal on the distal end. 74.The method of claim 51, wherein forming the connection joint includeselectroplating the connection joint on the routing line and the pad. 75.The method of claim 51, wherein forming the connection joint includeselectrolessly plating the connection joint on the routing line and thepad.
 76. The method of claim 51, wherein forming the connection jointincludes depositing a non-solidified material on the routing line andthe pad and then hardening the non-solidified material.
 77. The methodof claim 51, wherein forming the connection joint includes providing awire bond.
 78. The method of claim 51, including attaching the chip tothe routing line before welding the metal pillar to the routing line.79. The method of claim 51, including attaching the chip to the routingline after welding the metal pillar to the routing line.
 80. The methodof claim 51, including forming the connection joint before welding themetal pillar to the routing line.
 81. The method of claim 51, includingforming the connection joint after welding the metal pillar to therouting line.
 82. The method of claim 51, including forming theconnection joint before forming the encapsulant.
 83. The method of claim51, including forming the connection joint after forming theencapsulant.
 84. The method of claim 51, including forming theconnection joint before plating the plated contact terminal on thedistal end.
 85. The method of claim 51, including forming the connectionjoint after plating the plated contact terminal on the distal end. 86.The method of claim 51, including fracturing a wire after welding themetal pillar to the routing line and before forming the encapsulant,thereby detaching the wire from the stem.
 87. The method of claim 51,including providing an insulative base that contacts the routing line,is spaced from and overlapped by the chip and extends vertically beyondthe chip, the metal pillar and the encapsulant in the second direction.88. The method of claim 51, including providing an insulative adhesivethat attaches the chip to the routing line before forming theencapsulant.
 89. The method of claim 51, including providing a solderterminal that is electrically connected to the routing line, extendsvertically beyond the routing line and the encapsulant in the seconddirection and is spaced from the metal pillar and the connection joint.90. The method of claim 51, wherein the assembly is a first-levelpackage.
 91. A method of making a semiconductor chip assembly,comprising: providing a routing line; then mechanically attaching asemiconductor chip to the routing line, wherein the chip includes firstand second opposing surfaces, and the first surface of the chip includesa conductive pad; forming a connection joint that electrically connectsthe routing line and the pad; metallurgically welding a metal pillar toand only to the routing line by ball bonding using a capillary thatpresses a wire ball against the routing line, wherein the metal pillarconsists of a ball bond and an elongated stem, the ball bond is weldedto the routing line and the stem extends from the ball bond and isspaced from the routing line; forming an encapsulant after attaching thechip to the routing line and welding the metal pillar to the routingline, wherein the encapsulant includes a first surface that faces in afirst direction and a second surface that faces in a second directionopposite the first direction, the chip and the metal pillar are embeddedin the encapsulant, the encapsulant covers and extends vertically beyondthe chip, the routing line and the metal pillar in the first direction,the chip and the metal pillar extend vertically beyond the routing linein the first direction, the routing line extends laterally beyond themetal pillar towards the chip and extends vertically beyond the chip andthe metal pillar in the second direction, the metal pillar is disposedoutside a periphery of the chip and extends vertically across most orall of a thickness of the chip between the first and second surfaces ofthe chip, and the stem extends vertically beyond the ball bond in thefirst direction and extends vertically farther than the ball bond;removing a portion of the encapsulant by grinding the encapsulant andthen grinding the encapsulant and the stem such that a distal end of thestem is laterally aligned with the first surface of the encapsulant andexposed; and then plating a plated contact terminal on and only on thedistal end, wherein the plated contact terminal extends verticallybeyond the chip, the metal pillar and the encapsulant in the firstdirection, covers the distal end in the first direction, has a dome-likeshape with an apex that faces in the first direction and has a diameterthat is at least twice as large as a diameter of the distal end.
 92. Themethod of claim 91, wherein providing the routing line includesselectively depositing the routing line on a metal base, attaching thechip to the routing line includes positioning the chip such that themetal base extends vertically beyond the chip in the second direction,and after forming the encapsulant, etching the metal base therebyreducing contact area between the metal base and the routing line. 93.The method of claim 92, wherein etching the metal base forms a taperedpillar from an unetched portion of the metal base, and the taperedpillar contacts the routing line, is disposed outside the periphery ofthe chip, is overlapped by the metal pillar and extends verticallybeyond the chip, the routing line, the metal pillar and the encapsulantin the second direction.
 94. The method of claim 92, wherein etching themetal base eliminates contact area between the metal base and therouting line.
 95. The method of claim 92, wherein plating the platedcontact terminal on the distal end includes electroplating the platedcontact terminal on the distal end using the metal base, the routingline and the metal pillar as a plating bus before etching the metalbase.
 96. The method of claim 92, wherein plating the plated contactterminal on the distal end includes electrolessly plating the platedcontact terminal on the distal end after etching the metal base.
 97. Themethod of claim 91, wherein welding the metal pillar to the routing lineincludes thermosonic bonding.
 98. The method of claim 91, whereinremoving the portion of the encapsulant includes grinding theencapsulant without grinding the stem and without grinding the chip,then grinding the encapsulant and the stem without grinding the chip,and then grinding the encapsulant, the stem and the chip such that thesecond surface of the chip is laterally aligned with the first surfaceof the encapsulant and the distal end.
 99. The method of claim 91,wherein plating the plated contact terminal on the distal end includeselectroplating the plated contact terminal on the distal end.
 100. Themethod of claim 91, wherein plating the plated contact terminal on thedistal end includes electrolessly plating the plated contact terminal onthe distal end.
 101. The method of claim 91, including attaching thechip to the routing line before welding the metal pillar to the routingline.
 102. The method of claim 91, including attaching the chip to therouting line after welding the metal pillar to the routing line. 103.The method of claim 91, including forming the connection joint beforewelding the metal pillar to the routing line.
 104. The method of claim91, including forming the connection joint after welding the metalpillar to the routing line.
 105. The method of claim 91, includingforming the connection joint before forming the encapsulant.
 106. Themethod of claim 91, including forming the connection joint after formingthe encapsulant.
 107. The method of claim 91, including forming theconnection joint before plating the plated contact terminal on thedistal end.
 108. The method of claim 91, including forming theconnection joint after plating the plated contact terminal on the distalend.
 109. The method of claim 91, including fracturing a wire afterwelding the metal pillar to the routing line and before forming theencapsulant, thereby detaching the wire from the stem.
 110. The methodof claim 91, wherein the assembly is a first-level package.
 111. Amethod of making a semiconductor chip assembly, comprising: providing arouting line; then mechanically attaching a semiconductor chip to therouting line, wherein the chip includes first and second opposingsurfaces, and the first surface of the chip includes a conductive pad;forming a connection joint that electrically connects the routing lineand the pad; metallurgically welding a metal pillar to and only to therouting line by ball bonding using a capillary that presses a wire ballagainst the routing line, wherein the metal pillar consists of a ballbond and an elongated stem, the ball bond is welded to the routing lineand the stem extends from the ball bond and is spaced from the routingline; forming an encapsulant after attaching the chip to the routingline and welding the metal pillar to the routing line, wherein theencapsulant includes a first surface that faces in a first direction anda second surface that faces in a second direction opposite the firstdirection, the chip and the metal pillar are embedded in theencapsulant, the encapsulant covers and extends vertically beyond thechip, the routing line and the metal pillar in the first direction, thechip and the metal pillar extend vertically beyond the routing line inthe first direction, the routing line extends laterally beyond the metalpillar towards the chip and extends vertically beyond the chip and themetal pillar in the second direction, the metal pillar is disposedoutside a periphery of the chip and extends vertically across most orall of a thickness of the chip between the first and second surfaces ofthe chip, and the stem extends vertically beyond the ball bond in thefirst direction and extends vertically farther than the ball bond;removing a portion of the encapsulant by grinding the encapsulant andthen grinding the encapsulant and the stem such that a distal end of thestem is laterally aligned with the first surface of the encapsulant andexposed; and then plating a plated contact terminal on and only on thedistal end, wherein the metal pillar is disposed within a periphery ofthe routing line and a periphery of the plated contact terminal and doesnot contact any electrical conductor other than the routing line and theplated contact terminal, and the plated contact terminal extendsvertically beyond the chip, the metal pillar and the encapsulant in thefirst direction, covers the distal end in the first direction, has adome-like shape with an apex that faces in the first direction and has adiameter that is at least as large as a diameter of the ball bond atleast twice as large as a diameter of the distal end.
 112. The method ofclaim 111, wherein providing the routing line includes selectivelydepositing the routing line on a metal base, attaching the chip to therouting line includes positioning the chip such that the metal baseextends vertically beyond the chip in the second direction, and afterforming the encapsulant, etching the metal base thereby reducing contactarea between the metal base and the routing line.
 113. The method ofclaim 112, wherein etching the metal base forms a tapered pillar from anunetched portion of the metal base, and the tapered pillar contacts therouting line, is disposed outside the periphery of the chip, isoverlapped by the metal pillar and extends vertically beyond the chip,the routing line, the metal pillar and the encapsulant in the seconddirection.
 114. The method of claim 112, wherein etching the metal baseeliminates contact area between the metal base and the routing line.115. The method of claim 112, wherein plating the plated contactterminal on the distal end includes electroplating the plated contactterminal on the distal end using the metal base, the routing line andthe metal pillar as a plating bus before etching the metal base. 116.The method of claim 112, wherein plating the plated contact terminal onthe distal end includes electrolessly plating the plated contactterminal on the distal end after etching the metal base.
 117. The methodof claim 111, wherein welding the metal pillar to the routing lineincludes thermosonic bonding.
 118. The method of claim 111, whereinremoving the portion of the encapsulant includes grinding theencapsulant without grinding the stem and without grinding the chip,then grinding the encapsulant and the stem without grinding the chip,and then grinding the encapsulant, the stem and the chip such that thesecond surface of the chip is laterally aligned with the first surfaceof the encapsulant and the distal end.
 119. The method of claim 111,wherein plating the plated contact terminal on the distal end includeselectroplating the plated contact terminal on the distal end.
 120. Themethod of claim 111, wherein plating the plated contact terminal on thedistal end includes electrolessly plating the plated contact terminal onthe distal end.
 121. The method of claim 111, including attaching thechip to the routing line before welding the metal pillar to the routingline.
 122. The method of claim 111, including attaching the chip to therouting line after welding the metal pillar to the routing line. 123.The method of claim 111, including forming the connection joint beforewelding the metal pillar to the routing line.
 124. The method of claim111, including forming the connection joint after welding the metalpillar to the routing line.
 125. The method of claim 111, includingforming the connection joint before forming the encapsulant.
 126. Themethod of claim 111, including forming the connection joint afterforming the encapsulant.
 127. The method of claim 111, including formingthe connection joint before plating the plated contact terminal on thedistal end.
 128. The method of claim 111, including forming theconnection joint after plating the plated contact terminal on the distalend.
 129. The method of claim 111, including fracturing a wire afterwelding the metal pillar to the routing line and before forming theencapsulant, thereby detaching the wire from the stem.
 130. The methodof claim 111, wherein the assembly is a first-level package.